src/session_client.c

/**
 * \file session_client.c
 * \author Michal Vasko <mvasko@cesnet.cz>
 * \brief libnetconf2 session client functions
 *
 * Copyright (c) 2015 CESNET, z.s.p.o.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name of the Company nor the names of its contributors
 *    may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 */

#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <pthread.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <poll.h>

#include <libyang/libyang.h>

#include "libnetconf.h"
#include "session_client.h"
#include "messages_client.h"

static const char *ncds2str[] = {NULL, "config", "url", "running", "startup", "candidate"};

static struct nc_client_opts client_opts;

API int
nc_client_schema_searchpath(const char *path)
{
    if (client_opts.schema_searchpath) {
        free(client_opts.schema_searchpath);
    }

    if (path) {
        client_opts.schema_searchpath = strdup(path);
        if (!client_opts.schema_searchpath) {
            ERRMEM;
            return 1;
        }
    } else {
        client_opts.schema_searchpath = NULL;
    }

    return 0;
}

/* SCHEMAS_DIR not used (implicitly) */
static int
ctx_check_and_load_model(struct nc_session *session, const char *cpblt)
{
    const struct lys_module *module;
    char *ptr, *ptr2;
    char *model_name, *revision = NULL, *features = NULL;

    /* parse module */
    ptr = strstr(cpblt, "module=");
    if (!ptr) {
        ERR("Unknown capability \"%s\" could not be parsed.", cpblt);
        return -1;
    }
    ptr += 7;
    ptr2 = strchr(ptr, '&');
    if (!ptr2) {
        ptr2 = ptr + strlen(ptr);
    }
    model_name = strndup(ptr, ptr2 - ptr);

    /* parse revision */
    ptr = strstr(cpblt, "revision=");
    if (ptr) {
        ptr += 9;
        ptr2 = strchr(ptr, '&');
        if (!ptr2) {
            ptr2 = ptr + strlen(ptr);
        }
        revision = strndup(ptr, ptr2 - ptr);
    }

    /* load module if needed */
    module = ly_ctx_get_module(session->ctx, model_name, revision);
    if (!module) {
        module = ly_ctx_load_module(session->ctx, model_name, revision);
    }

    free(revision);
    if (!module) {
        WRN("Failed to load model \"%s\".", model_name);
        free(model_name);
        return 1;
    }
    free(model_name);

    /* parse features */
    ptr = strstr(cpblt, "features=");
    if (ptr) {
        ptr += 9;
        ptr2 = strchr(ptr, '&');
        if (!ptr2) {
            ptr2 = ptr + strlen(ptr);
        }
        features = strndup(ptr, ptr2 - ptr);
    }

    /* enable features */
    if (features) {
        /* basically manual strtok_r (to avoid macro) */
        ptr2 = features;
        for (ptr = features; *ptr; ++ptr) {
            if (*ptr == ',') {
                *ptr = '\0';
                /* remember last feature */
                ptr2 = ptr + 1;
            }
        }

        ptr = features;
        lys_features_enable(module, ptr);
        while (ptr != ptr2) {
            ptr += strlen(ptr) + 1;
            lys_features_enable(module, ptr);
        }

        free(features);
    }

    return 0;
}

/* SCHEMAS_DIR used */
static int
ctx_check_and_load_ietf_netconf(struct ly_ctx *ctx, const char **cpblts, int from_file)
{
    int i;
    const struct lys_module *ietfnc;

    ietfnc = ly_ctx_get_module(ctx, "ietf-netconf", NULL);
    if (!ietfnc) {
        if (from_file) {
            ietfnc = lys_parse_path(ctx, SCHEMAS_DIR"/ietf-netconf.yin", LYS_IN_YIN);
        } else {
            ietfnc = ly_ctx_load_module(ctx, "ietf-netconf", NULL);
        }
    }
    if (!ietfnc) {
        ERR("Loading base NETCONF schema failed.");
        return 1;
    }

    /* set supported capabilities from ietf-netconf */
    for (i = 0; cpblts[i]; ++i) {
        if (!strncmp(cpblts[i], "urn:ietf:params:netconf:capability:", 35)) {
            if (!strncmp(cpblts[i] + 35, "writable-running", 16)) {
                lys_features_enable(ietfnc, "writable-running");
            } else if (!strncmp(cpblts[i] + 35, "candidate", 9)) {
                lys_features_enable(ietfnc, "candidate");
            } else if (!strcmp(cpblts[i] + 35, "confirmed-commit:1.1")) {
                lys_features_enable(ietfnc, "confirmed-commit");
            } else if (!strncmp(cpblts[i] + 35, "rollback-on-error", 17)) {
                lys_features_enable(ietfnc, "rollback-on-error");
            } else if (!strcmp(cpblts[i] + 35, "validate:1.1")) {
                lys_features_enable(ietfnc, "validate");
            } else if (!strncmp(cpblts[i] + 35, "startup", 7)) {
                lys_features_enable(ietfnc, "startup");
            } else if (!strncmp(cpblts[i] + 35, "url", 3)) {
                lys_features_enable(ietfnc, "url");
            } else if (!strncmp(cpblts[i] + 35, "xpath", 5)) {
                lys_features_enable(ietfnc, "xpath");
            }
        }
    }

    return 0;
}

static char *
libyang_module_clb(const char *name, const char *revision, void *user_data, LYS_INFORMAT *format,
                   void (**free_model_data)(char *model_data))
{
    struct nc_session *session = (struct nc_session *)user_data;
    struct nc_rpc *rpc;
    struct nc_reply *reply;
    struct nc_reply_data *data_rpl;
    NC_MSG_TYPE msg;
    char *model_data = NULL, *ptr, *ptr2, *anyxml;
    uint64_t msgid;

    /* TODO later replace with yang to reduce model size? */
    rpc = nc_rpc_getschema(name, revision, "yin", NC_PARAMTYPE_CONST);
    *format = LYS_IN_YIN;

    while ((msg = nc_send_rpc(session, rpc, 0, &msgid)) == NC_MSG_WOULDBLOCK) {
        usleep(1000);
    }
    if (msg == NC_MSG_ERROR) {
        ERR("Session %u: failed to send the <get-schema> RPC.", session->id);
        nc_rpc_free(rpc);
        return NULL;
    }

    msg = nc_recv_reply(session, rpc, msgid, 250, &reply);
    nc_rpc_free(rpc);
    if (msg == NC_MSG_WOULDBLOCK) {
        ERR("Session %u: timeout for receiving reply to a <get-schema> expired.", session->id);
        return NULL;
    } else if (msg == NC_MSG_ERROR) {
        ERR("Session %u: failed to receive a reply to <get-schema>.", session->id);
        return NULL;
    }

    if (reply->type != NC_RPL_DATA) {
        /* TODO print the error, if error */
        ERR("Session %u: unexpected reply type to a <get-schema> RPC.", session->id);
        nc_reply_free(reply);
        return NULL;
    }

    data_rpl = (struct nc_reply_data *)reply;
    anyxml = lyxml_serialize(((struct lyd_node_anyxml *)data_rpl->data)->value);
    nc_reply_free(reply);
    *free_model_data = NULL;

    /* it's with the data root node, remove it */
    if (anyxml) {
        ptr = strchr(anyxml, '>');
        ++ptr;

        ptr2 = strrchr(anyxml, '<');

        model_data = strndup(ptr, strlen(ptr) - strlen(ptr2));
        free(anyxml);
    }

    return model_data;
}

/* return 0 - ok, 1 - some models failed to load, -1 - error */
int
nc_ctx_check_and_fill(struct nc_session *session)
{
    int i, get_schema_support = 0, ret = 0, r;
    ly_module_clb old_clb = NULL;
    void *old_data = NULL;

    assert(session->cpblts && session->ctx);

    /* check if get-schema is supported */
    for (i = 0; session->cpblts[i]; ++i) {
        if (!strncmp(session->cpblts[i], "urn:ietf:params:xml:ns:yang:ietf-netconf-monitoring", 51)) {
            get_schema_support = 1;
            break;
        }
    }

    /* get-schema is supported, load local ietf-netconf-monitoring so we can create <get-schema> RPCs */
    if (get_schema_support && !ly_ctx_get_module(session->ctx, "ietf-netconf-monitoring", NULL)) {
        if (lys_parse_path(session->ctx, SCHEMAS_DIR"/ietf-netconf-monitoring.yin", LYS_IN_YIN)) {
            /* set module retrieval using <get-schema> */
            old_clb = ly_ctx_get_module_clb(session->ctx, &old_data);
            ly_ctx_set_module_clb(session->ctx, &libyang_module_clb, session);
        } else {
            WRN("Loading NETCONF monitoring schema failed, cannot use <get-schema>.");
        }
    }

    /* load base model disregarding whether it's in capabilities (but NETCONF capabilities are used to enable features) */
    if (ctx_check_and_load_ietf_netconf(session->ctx, session->cpblts, !get_schema_support)) {
        if (old_clb) {
            ly_ctx_set_module_clb(session->ctx, old_clb, old_data);
        }
        return -1;
    }

    /* load all other models */
    for (i = 0; session->cpblts[i]; ++i) {
        if (!strncmp(session->cpblts[i], "urn:ietf:params:netconf:capability", 34)
                || !strncmp(session->cpblts[i], "urn:ietf:params:netconf:base", 28)) {
            continue;
        }

        r = ctx_check_and_load_model(session, session->cpblts[i]);
        if (r == -1) {
            ret = -1;
            break;
        }

        /* failed to load schema, but let's try to find it using user callback (or locally, if not set),
         * if it was using get-schema */
        if (r == 1) {
            if (get_schema_support) {
                VRB("Trying to load the schema from a different source.");
                /* works even if old_clb is NULL */
                ly_ctx_set_module_clb(session->ctx, old_clb, old_data);
                r = ctx_check_and_load_model(session, session->cpblts[i]);
            }

            /* fail again (or no other way to try), too bad */
            if (r) {
                ret = 1;
            }

            /* set get-schema callback back */
            ly_ctx_set_module_clb(session->ctx, &libyang_module_clb, session);
        }
    }

    if (old_clb) {
        ly_ctx_set_module_clb(session->ctx, old_clb, old_data);
    }
    if (ret == 1) {
        WRN("Some models failed to be loaded, any data from these models will be ignored.");
    }
    return ret;
}

API struct nc_session *
nc_connect_inout(int fdin, int fdout, struct ly_ctx *ctx)
{
    struct nc_session *session;

    if ((fdin < 0) || (fdout < 0)) {
        ERRARG;
        return NULL;
    }

    /* prepare session structure */
    session = calloc(1, sizeof *session);
    if (!session) {
        ERRMEM;
        return NULL;
    }
    session->status = NC_STATUS_STARTING;
    session->side = NC_CLIENT;

    /* transport specific data */
    session->ti_type = NC_TI_FD;
    session->ti.fd.in = fdin;
    session->ti.fd.out = fdout;

    /* assign context (dicionary needed for handshake) */
    if (!ctx) {
        ctx = ly_ctx_new(SCHEMAS_DIR);
    } else {
        session->flags |= NC_SESSION_SHAREDCTX;
    }
    session->ctx = ctx;

    /* NETCONF handshake */
    if (nc_handshake(session)) {
        goto fail;
    }
    session->status = NC_STATUS_RUNNING;

    if (nc_ctx_check_and_fill(session) == -1) {
        goto fail;
    }

    return session;

fail:
    nc_session_free(session);
    return NULL;
}

int
nc_sock_connect(const char* host, uint16_t port)
{
    int i, sock = -1;
    struct addrinfo hints, *res_list, *res;
    char port_s[6]; /* length of string representation of short int */

    snprintf(port_s, 6, "%u", port);

    /* Connect to a server */
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;
    i = getaddrinfo(host, port_s, &hints, &res_list);
    if (i != 0) {
        ERR("Unable to translate the host address (%s).", gai_strerror(i));
        return -1;
    }

    for (i = 0, res = res_list; res != NULL; res = res->ai_next) {
        sock = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
        if (sock == -1) {
            /* socket was not created, try another resource */
            i = errno;
            goto errloop;
        }

        if (connect(sock, res->ai_addr, res->ai_addrlen) == -1) {
            /* network connection failed, try another resource */
            i = errno;
            close(sock);
            sock = -1;
            goto errloop;
        }

        /* we're done, network connection established */
        break;
errloop:
        VRB("Unable to connect to %s:%s over %s (%s).", host, port_s,
            (res->ai_family == AF_INET6) ? "IPv6" : "IPv4", strerror(i));
        continue;
    }

    if (sock == -1) {
        ERR("Unable to connect to %s:%s.", host, port_s);
    } else {
        VRB("Successfully connected to %s:%s over %s.", host, port_s, (res->ai_family == AF_INET6) ? "IPv6" : "IPv4");
    }
    freeaddrinfo(res_list);

    return sock;
}

static NC_MSG_TYPE
get_msg(struct nc_session *session, int timeout, uint64_t msgid, struct lyxml_elem **msg)
{
    int r, elapsed = 0;
    char *ptr;
    const char *str_msgid;
    uint64_t cur_msgid;
    struct lyxml_elem *xml;
    struct nc_msg_cont *cont, **cont_ptr;
    NC_MSG_TYPE msgtype = 0; /* NC_MSG_ERROR */

    r = nc_timedlock(session->ti_lock, timeout, &elapsed);
    if (r == -1) {
        /* error */
        return NC_MSG_ERROR;
    } else if (!r) {
        /* timeout */
        return NC_MSG_WOULDBLOCK;
    }
    if (timeout > 0) {
        timeout -= elapsed;
    }

    /* try to get notification from the session's queue */
    if (!msgid && session->notifs) {
        cont = session->notifs;
        session->notifs = cont->next;

        pthread_mutex_unlock(session->ti_lock);

        *msg = cont->msg;
        free(cont);

        return NC_MSG_NOTIF;
    }

    /* try to get rpc-reply from the session's queue */
    if (msgid && session->replies) {
        while (session->replies) {
            cont = session->replies;
            session->replies = cont->next;

            str_msgid = lyxml_get_attr(cont->msg, "message-id", NULL);
            cur_msgid = strtoul(str_msgid, &ptr, 10);

            if (cur_msgid == msgid) {
                session->replies = cont->next;
                pthread_mutex_unlock(session->ti_lock);

                *msg = cont->msg;
                free(cont);

                return NC_MSG_REPLY;
            }

            ERR("Session %u: discarding a <rpc-reply> with an unexpected message-id \"%s\".", str_msgid);
            lyxml_free(session->ctx, cont->msg);
            free(msg);
        }
    }

    /* read message from wire */
    msgtype = nc_read_msg_poll(session, timeout, &xml);

    /* we read rpc-reply, want a notif */
    if (!msgid && (msgtype == NC_MSG_REPLY)) {
        /* just check that there is a message-id */
        str_msgid = lyxml_get_attr(xml, "message-id", NULL);
        if (!str_msgid) {
            pthread_mutex_unlock(session->ti_lock);
            ERR("Session %u: received a <rpc-reply> with no message-id, discarding.", session->id);
            lyxml_free(session->ctx, xml);
            return NC_MSG_ERROR;
        }

        cont_ptr = &session->replies;
        while (*cont_ptr) {
            cont_ptr = &((*cont_ptr)->next);
        }
        *cont_ptr = malloc(sizeof **cont_ptr);
        (*cont_ptr)->msg = xml;
        (*cont_ptr)->next = NULL;
    }

    /* we read notif, want a rpc-reply */
    if (msgid && (msgtype == NC_MSG_NOTIF)) {
        /* TODO check whether the session is even subscribed */
        /*if (!session->notif) {
            pthread_mutex_unlock(session->ti_lock);
            ERR("Session %u: received a <notification> but session is not subscribed.", session->id);
            lyxml_free(session->ctx, xml);
            return NC_MSG_ERROR;
        }*/

        cont_ptr = &session->notifs;
        while (*cont_ptr) {
            cont_ptr = &((*cont_ptr)->next);
        }
        *cont_ptr = malloc(sizeof **cont_ptr);
        (*cont_ptr)->msg = xml;
        (*cont_ptr)->next = NULL;
    }

    pthread_mutex_unlock(session->ti_lock);

    switch (msgtype) {
    case NC_MSG_NOTIF:
        if (!msgid) {
            *msg = xml;
        }
        break;

    case NC_MSG_REPLY:
        if (msgid) {
            *msg = xml;
        }
        break;

    case NC_MSG_HELLO:
        ERR("Session %u: received another <hello> message.", session->id);
        lyxml_free(session->ctx, xml);
        return NC_MSG_ERROR;

    case NC_MSG_RPC:
        ERR("Session %u: received <rpc> from a NETCONF server.", session->id);
        lyxml_free(session->ctx, xml);
        return NC_MSG_ERROR;

    default:
        /* NC_MSG_WOULDBLOCK and NC_MSG_ERROR - pass it out;
         * NC_MSG_NONE is not returned by nc_read_msg()
         */
        break;
    }

    return msgtype;
}

/* cannot strictly fail, but does not need to fill any error parameter at all */
static void
parse_rpc_error(struct ly_ctx *ctx, struct lyxml_elem *xml, struct nc_err *err)
{
    struct lyxml_elem *iter, *next, *info;

    LY_TREE_FOR(xml->child, iter) {
        if (!iter->ns) {
            if (iter->content) {
                WRN("<rpc-error> child \"%s\" with value \"%s\" without namespace.", iter->name, iter->content);
            } else {
                WRN("<rpc-error> child \"%s\" without namespace.", iter->name);
            }
            continue;
        } else if (strcmp(iter->ns->value, NC_NS_BASE)) {
            if (iter->content) {
                WRN("<rpc-error> child \"%s\" with value \"%s\" in an unknown namespace \"%s\".",
                    iter->name, iter->content, iter->ns->value);
            } else {
                WRN("<rpc-error> child \"%s\" in an unknown namespace \"%s\".", iter->name, iter->ns->value);
            }
            continue;
        }

        if (!strcmp(iter->name, "error-type")) {
            if (!iter->content || (strcmp(iter->content, "transport") && strcmp(iter->content, "rpc")
                    && strcmp(iter->content, "protocol") && strcmp(iter->content, "application"))) {
                WRN("<rpc-error> <error-type> unknown value \"%s\".", (iter->content ? iter->content : ""));
            } else if (err->type) {
                WRN("<rpc-error> <error-type> duplicated.");
            } else {
                err->type = lydict_insert(ctx, iter->content, 0);
            }
        } else if (!strcmp(iter->name, "error-tag")) {
            if (!iter->content || (strcmp(iter->content, "in-use") && strcmp(iter->content, "invalid-value")
                    && strcmp(iter->content, "too-big") && strcmp(iter->content, "missing-attribute")
                    && strcmp(iter->content, "bad-attribute") && strcmp(iter->content, "unknown-attribute")
                    && strcmp(iter->content, "missing-element") && strcmp(iter->content, "bad-element")
                    && strcmp(iter->content, "unknown-element") && strcmp(iter->content, "unknown-namespace")
                    && strcmp(iter->content, "access-denied") && strcmp(iter->content, "lock-denied")
                    && strcmp(iter->content, "resource-denied") && strcmp(iter->content, "rollback-failed")
                    && strcmp(iter->content, "data-exists") && strcmp(iter->content, "data-missing")
                    && strcmp(iter->content, "operation-not-supported") && strcmp(iter->content, "operation-failed")
                    && strcmp(iter->content, "malformed-message"))) {
                WRN("<rpc-error> <error-tag> unknown value \"%s\".", (iter->content ? iter->content : ""));
            } else if (err->tag) {
                WRN("<rpc-error> <error-tag> duplicated.");
            } else {
                err->tag = lydict_insert(ctx, iter->content, 0);
            }
        } else if (!strcmp(iter->name, "error-severity")) {
            if (!iter->content || (strcmp(iter->content, "error") && strcmp(iter->content, "warning"))) {
                WRN("<rpc-error> <error-severity> unknown value \"%s\".", (iter->content ? iter->content : ""));
            } else if (err->severity) {
                WRN("<rpc-error> <error-severity> duplicated.");
            } else {
                err->severity = lydict_insert(ctx, iter->content, 0);
            }
        } else if (!strcmp(iter->name, "error-app-tag")) {
            if (err->apptag) {
                WRN("<rpc-error> <error-app-tag> duplicated.");
            } else {
                err->apptag = lydict_insert(ctx, (iter->content ? iter->content : ""), 0);
            }
        } else if (!strcmp(iter->name, "error-path")) {
            if (err->path) {
                WRN("<rpc-error> <error-path> duplicated.");
            } else {
                err->path = lydict_insert(ctx, (iter->content ? iter->content : ""), 0);
            }
        } else if (!strcmp(iter->name, "error-message")) {
            if (err->message) {
                WRN("<rpc-error> <error-message> duplicated.");
            } else {
                err->message_lang = lyxml_get_attr(iter, "xml:lang", NULL);
                if (!err->message_lang) {
                    VRB("<rpc-error> <error-message> without the recommended \"xml:lang\" attribute.");
                }
                err->message = lydict_insert(ctx, (iter->content ? iter->content : ""), 0);
            }
        } else if (!strcmp(iter->name, "error-info")) {
            LY_TREE_FOR_SAFE(iter->child, next, info) {
                if (info->ns && !strcmp(info->ns->value, NC_NS_BASE)) {
                    if (!strcmp(info->name, "session-id")) {
                        if (err->sid) {
                            WRN("<rpc-error> <error-info> <session-id> duplicated.");
                        } else {
                            err->sid = lydict_insert(ctx, (info->content ? info->content : ""), 0);
                        }
                    } else if (!strcmp(info->name, "bad-attr")) {
                        ++err->attr_count;
                        err->attr = realloc(err->attr, err->attr_count * sizeof *err->attr);
                        err->attr[err->attr_count - 1] = lydict_insert(ctx, (info->content ? info->content : ""), 0);
                    } else if (!strcmp(info->name, "bad-element")) {
                        ++err->elem_count;
                        err->elem = realloc(err->elem, err->elem_count * sizeof *err->elem);
                        err->elem[err->elem_count - 1] = lydict_insert(ctx, (info->content ? info->content : ""), 0);
                    } else if (!strcmp(info->name, "bad-namespace")) {
                        ++err->ns_count;
                        err->ns = realloc(err->ns, err->ns_count * sizeof *err->ns);
                        err->ns[err->ns_count - 1] = lydict_insert(ctx, (info->content ? info->content : ""), 0);
                    } else {
                        if (info->content) {
                            WRN("<rpc-error> <error-info> unknown child \"%s\" with value \"%s\".",
                                info->name, info->content);
                        } else {
                            WRN("<rpc-error> <error-info> unknown child \"%s\".", info->name);
                        }
                    }
                } else {
                    lyxml_unlink(ctx, info);
                    ++err->other_count;
                    err->other = realloc(err->other, err->other_count * sizeof *err->other);
                    err->other[err->other_count - 1] = info;
                }
            }
        } else {
            if (iter->content) {
                WRN("<rpc-error> unknown child \"%s\" with value \"%s\".", iter->name, iter->content);
            } else {
                WRN("<rpc-error> unknown child \"%s\".", iter->name);
            }
        }
    }
}

static struct nc_reply *
parse_reply(struct ly_ctx *ctx, struct lyxml_elem *xml, struct nc_rpc *rpc)
{
    struct lyxml_elem *iter;
    const struct lys_node *schema = NULL;
    const struct lys_module *mod;
    struct lyd_node *data = NULL;
    struct nc_client_reply_error *error_rpl;
    struct nc_reply_data *data_rpl;
    struct nc_reply *reply = NULL;
    struct nc_rpc_generic *rpc_gen;
    int i;

    if (!xml->child) {
        ERR("An empty <rpc-reply>.");
        return NULL;
    }

    /* rpc-error */
    if (!strcmp(xml->child->name, "rpc-error") && xml->child->ns && !strcmp(xml->child->ns->value, NC_NS_BASE)) {
        /* count and check elements */
        i = 0;
        LY_TREE_FOR(xml->child, iter) {
            if (strcmp(iter->name, "rpc-error")) {
                ERR("<rpc-reply> content mismatch (<rpc-error> and <%s>).", iter->name);
                return NULL;
            } else if (!iter->ns) {
                ERR("<rpc-reply> content mismatch (<rpc-error> without namespace).");
                return NULL;
            } else if (strcmp(iter->ns->value, NC_NS_BASE)) {
                ERR("<rpc-reply> content mismatch (<rpc-error> with NS \"%s\").", iter->ns->value);
                return NULL;
            }
            ++i;
        }

        error_rpl = malloc(sizeof *error_rpl);
        error_rpl->type = NC_RPL_ERROR;
        error_rpl->err = calloc(i, sizeof *error_rpl->err);
        error_rpl->count = i;
        error_rpl->ctx = ctx;
        reply = (struct nc_reply *)error_rpl;

        i = 0;
        LY_TREE_FOR(xml->child, iter) {
            parse_rpc_error(ctx, iter, error_rpl->err + i);
            ++i;
        }

    /* ok */
    } else if (!strcmp(xml->child->name, "ok") && xml->child->ns && !strcmp(xml->child->ns->value, NC_NS_BASE)) {
        if (xml->child->next) {
            ERR("<rpc-reply> content mismatch (<ok> and <%s>).", xml->child->next->name);
            return NULL;
        }
        reply = malloc(sizeof *reply);
        reply->type = NC_RPL_OK;

    /* some RPC output */
    } else {
        switch (rpc->type) {
        case NC_RPC_GENERIC:
            rpc_gen = (struct nc_rpc_generic *)rpc;

            if (rpc_gen->has_data) {
                schema = rpc_gen->content.data->schema;
            } else {
                data = lyd_parse_data(ctx, rpc_gen->content.xml_str, LYD_XML, LYD_OPT_RPC);
                if (!data) {
                    ERR("Failed to parse a generic RPC XML.");
                    return NULL;
                }
                schema = data->schema;
                lyd_free(data);
                data = NULL;
            }
            if (!schema) {
                ERRINT;
                return NULL;
            }
            break;

        case NC_RPC_GETCONFIG:
        case NC_RPC_GET:
            /* special treatment */
            data = lyd_parse_xml(ctx, &xml->child->child, LYD_OPT_DESTRUCT
                                 | (rpc->type == NC_RPC_GETCONFIG ? LYD_OPT_GETCONFIG : LYD_OPT_GET));
            if (!data) {
                ERR("Failed to parse <%s> reply.", (rpc->type == NC_RPC_GETCONFIG ? "get-config" : "get"));
                return NULL;
            }
            break;

        case NC_RPC_GETSCHEMA:
            mod = ly_ctx_get_module(ctx, "ietf-netconf-monitoring", NULL);
            if (mod) {
                schema = lys_get_node(mod, "/get-schema");
            }
            if (!schema) {
                ERRINT;
                return NULL;
            }
            break;

        case NC_RPC_EDIT:
        case NC_RPC_COPY:
        case NC_RPC_DELETE:
        case NC_RPC_LOCK:
        case NC_RPC_UNLOCK:
        case NC_RPC_KILL:
        case NC_RPC_COMMIT:
        case NC_RPC_DISCARD:
        case NC_RPC_CANCEL:
        case NC_RPC_VALIDATE:
        case NC_RPC_SUBSCRIBE:
            /* there is no output defined */
            ERR("Unexpected data reply (root elem \"%s\").", xml->child->name);
            return NULL;
        default:
            ERRINT;
            return NULL;
        }

        data_rpl = malloc(sizeof *data_rpl);
        data_rpl->type = NC_RPL_DATA;
        if (!data) {
            data_rpl->data = lyd_parse_xml(ctx, &xml->child, LYD_OPT_DESTRUCT | LYD_OPT_RPCREPLY, schema);
        } else {
            /* <get>, <get-config> */
            data_rpl->data = data;
        }
        if (!data_rpl->data) {
            ERR("Failed to parse <rpc-reply>.");
            free(data_rpl);
            return NULL;
        }
        reply = (struct nc_reply *)data_rpl;
    }

    return reply;
}

#if defined(ENABLE_SSH) || defined(ENABLE_TLS)

int
nc_client_ch_add_bind_listen(const char *address, uint16_t port, NC_TRANSPORT_IMPL ti)
{
    int sock;

    if (!address || !port) {
        ERRARG;
        return -1;
    }

    sock = nc_sock_listen(address, port);
    if (sock == -1) {
        return -1;
    }

    ++client_opts.ch_bind_count;
    client_opts.ch_binds = realloc(client_opts.ch_binds, client_opts.ch_bind_count * sizeof *client_opts.ch_binds);

    client_opts.ch_binds[client_opts.ch_bind_count - 1].address = strdup(address);
    client_opts.ch_binds[client_opts.ch_bind_count - 1].port = port;
    client_opts.ch_binds[client_opts.ch_bind_count - 1].sock = sock;
    client_opts.ch_binds[client_opts.ch_bind_count - 1].ti = ti;

    return 0;
}

int
nc_client_ch_del_bind(const char *address, uint16_t port, NC_TRANSPORT_IMPL ti)
{
    uint32_t i;
    int ret = -1;

    if (!address && !port && !ti) {
        for (i = 0; i < client_opts.ch_bind_count; ++i) {
            close(client_opts.ch_binds[i].sock);
            free((char *)client_opts.ch_binds[i].address);

            ret = 0;
        }
        free(client_opts.ch_binds);
        client_opts.ch_binds = NULL;
        client_opts.ch_bind_count = 0;
    } else {
        for (i = 0; i < client_opts.ch_bind_count; ++i) {
            if ((!address || !strcmp(client_opts.ch_binds[i].address, address))
                    && (!port || (client_opts.ch_binds[i].port == port))
                    && (!ti || (client_opts.ch_binds[i].ti == ti))) {
                close(client_opts.ch_binds[i].sock);
                free((char *)client_opts.ch_binds[i].address);

                --client_opts.ch_bind_count;
                memcpy(&client_opts.ch_binds[i], &client_opts.ch_binds[client_opts.ch_bind_count], sizeof *client_opts.ch_binds);

                ret = 0;
            }
        }
    }

    return ret;
}

API int
nc_accept_callhome(int timeout, struct ly_ctx *ctx, struct nc_session **session)
{
    int sock;
    char *host = NULL;
    uint16_t port, idx;

    if (!client_opts.ch_binds || !session) {
        ERRARG;
        return -1;
    }

    sock = nc_sock_accept_binds(client_opts.ch_binds, client_opts.ch_bind_count, timeout, &host, &port, &idx);

    if (sock < 1) {
        return sock;
    }

#ifdef ENABLE_SSH
    if (client_opts.ch_binds[idx].ti == NC_TI_LIBSSH) {
        *session = nc_accept_callhome_ssh_sock(sock, host, port, ctx);
    } else
#endif
#ifdef ENABLE_TLS
    if (client_opts.ch_binds[idx].ti == NC_TI_OPENSSL) {
        *session = nc_accept_callhome_tls_sock(sock, host, port, ctx);
    } else
#endif
    {
        *session = NULL;
    }

    free(host);

    if (!(*session)) {
        return -1;
    }

    return 1;
}

#endif /* ENABLE_SSH || ENABLE_TLS */

API NC_MSG_TYPE
nc_recv_reply(struct nc_session *session, struct nc_rpc *rpc, uint64_t msgid, int timeout, struct nc_reply **reply)
{
    struct lyxml_elem *xml;
    NC_MSG_TYPE msgtype = 0; /* NC_MSG_ERROR */

    if (!session || !rpc || !reply) {
        ERRARG;
        return NC_MSG_ERROR;
    } else if ((session->status != NC_STATUS_RUNNING) || (session->side != NC_CLIENT)) {
        ERR("Session %u: invalid session to receive RPC replies.", session->id);
        return NC_MSG_ERROR;
    }
    *reply = NULL;

    msgtype = get_msg(session, timeout, msgid, &xml);

    if (msgtype == NC_MSG_REPLY) {
        *reply = parse_reply(session->ctx, xml, rpc);
        lyxml_free(session->ctx, xml);
        if (!(*reply)) {
            return NC_MSG_ERROR;
        }
    }

    return msgtype;
}

API NC_MSG_TYPE
nc_recv_notif(struct nc_session *session, int timeout, struct nc_notif **notif)
{
    struct lyxml_elem *xml, *ev_time;
    NC_MSG_TYPE msgtype = 0; /* NC_MSG_ERROR */

    if (!session || !notif) {
        ERRARG;
        return NC_MSG_ERROR;
    } else if (session->status != NC_STATUS_RUNNING || session->side != NC_CLIENT) {
        ERR("Session %u: invalid session to receive Notifications.", session->id);
        return NC_MSG_ERROR;
    }

    msgtype = get_msg(session, timeout, 0, &xml);

    if (msgtype == NC_MSG_NOTIF) {
        *notif = calloc(1, sizeof **notif);

        /* eventTime */
        LY_TREE_FOR(xml->child, ev_time) {
            if (!strcmp(ev_time->name, "eventTime")) {
                (*notif)->datetime = lydict_insert(session->ctx, ev_time->content, 0);
                /* lyd_parse does not know this element */
                lyxml_free(session->ctx, ev_time);
                break;
            }
        }
        if (!(*notif)->datetime) {
            ERR("Session %u: notification is missing the \"eventTime\" element.", session->id);
            goto fail;
        }

        /* notification body */
        (*notif)->tree = lyd_parse_xml(session->ctx, &xml->child, LYD_OPT_DESTRUCT | LYD_OPT_NOTIF);
        lyxml_free(session->ctx, xml);
        xml = NULL;
        if (!(*notif)->tree) {
            ERR("Session %u: failed to parse a new notification.", session->id);
            goto fail;
        }
    }

    return msgtype;

fail:
    lydict_remove(session->ctx, (*notif)->datetime);
    lyd_free((*notif)->tree);
    free(*notif);
    *notif = NULL;
    lyxml_free(session->ctx, xml);

    return NC_MSG_ERROR;
}

static void *
nc_recv_notif_thread(void *arg)
{
    struct nc_ntf_thread_arg *ntarg;
    struct nc_session *session;
    void (*notif_clb)(struct nc_session *session, const struct nc_notif *notif);
    struct nc_notif *notif;
    NC_MSG_TYPE msgtype;

    ntarg = (struct nc_ntf_thread_arg *)arg;
    session = ntarg->session;
    notif_clb = ntarg->notif_clb;
    free(ntarg);

    while (session->ntf_tid) {
        msgtype = nc_recv_notif(session, 0, &notif);
        if (msgtype == NC_MSG_NOTIF) {
            notif_clb(session, notif);
            if (!strcmp(notif->tree->schema->name, "notificationComplete")
                    && !strcmp(notif->tree->schema->module->name, "nc-notifications")) {
                nc_notif_free(notif);
                break;
            }
            nc_notif_free(notif);
        }

        usleep(NC_CLIENT_NOTIF_THREAD_SLEEP);
    }

    return NULL;
}

API int
nc_recv_notif_dispatch(struct nc_session *session, void (*notif_clb)(struct nc_session *session, const struct nc_notif *notif))
{
    struct nc_ntf_thread_arg *ntarg;
    int ret;

    if (!session || !notif_clb) {
        ERRARG;
        return -1;
    } else if ((session->status != NC_STATUS_RUNNING) || (session->side != NC_CLIENT)) {
        ERR("Session %u: invalid session to receive Notifications.", session->id);
        return -1;
    } else if (session->ntf_tid) {
        ERR("Session %u: separate notification thread is already running.", session->id);
        return -1;
    }

    ntarg = malloc(sizeof *ntarg);
    ntarg->session = session;
    ntarg->notif_clb = notif_clb;

    /* just so that nc_recv_notif_thread() does not immediately exit, the value does not matter */
    session->ntf_tid = malloc(sizeof *session->ntf_tid);

    ret = pthread_create((pthread_t *)session->ntf_tid, NULL, nc_recv_notif_thread, ntarg);
    if (ret) {
        ERR("Session %u: failed to create a new thread (%s).", strerror(errno));
        free(ntarg);
        free((pthread_t *)session->ntf_tid);
        session->ntf_tid = NULL;
        return -1;
    }

    return 0;
}

API NC_MSG_TYPE
nc_send_rpc(struct nc_session *session, struct nc_rpc *rpc, int timeout, uint64_t *msgid)
{
    NC_MSG_TYPE r;
    int ret;
    struct nc_rpc_generic *rpc_gen;
    struct nc_rpc_getconfig *rpc_gc;
    struct nc_rpc_edit *rpc_e;
    struct nc_rpc_copy *rpc_cp;
    struct nc_rpc_delete *rpc_del;
    struct nc_rpc_lock *rpc_lock;
    struct nc_rpc_get *rpc_g;
    struct nc_rpc_kill *rpc_k;
    struct nc_rpc_commit *rpc_com;
    struct nc_rpc_cancel *rpc_can;
    struct nc_rpc_validate *rpc_val;
    struct nc_rpc_getschema *rpc_gs;
    struct nc_rpc_subscribe *rpc_sub;
    struct lyd_node *data, *node;
    const struct lys_module *ietfnc, *ietfncmon, *notifs, *ietfncwd = NULL;
    char str[11];
    uint64_t cur_msgid;

    if (!session || !rpc || !msgid) {
        ERRARG;
        return NC_MSG_ERROR;
    } else if (session->status != NC_STATUS_RUNNING || session->side != NC_CLIENT) {
        ERR("Session %u: invalid session to send RPCs.", session->id);
        return NC_MSG_ERROR;
    }

    if ((rpc->type != NC_RPC_GETSCHEMA) && (rpc->type != NC_RPC_GENERIC) && (rpc->type != NC_RPC_SUBSCRIBE)) {
        ietfnc = ly_ctx_get_module(session->ctx, "ietf-netconf", NULL);
        if (!ietfnc) {
            ERR("Session %u: missing ietf-netconf schema in the context.", session->id);
            return NC_MSG_ERROR;
        }
    }

    switch (rpc->type) {
    case NC_RPC_GENERIC:
        rpc_gen = (struct nc_rpc_generic *)rpc;

        if (rpc_gen->has_data) {
            data = rpc_gen->content.data;
        } else {
            data = lyd_parse_data(session->ctx, rpc_gen->content.xml_str, LYD_XML, LYD_OPT_STRICT);
        }
        break;

    case NC_RPC_GETCONFIG:
        rpc_gc = (struct nc_rpc_getconfig *)rpc;

        data = lyd_new(NULL, ietfnc, "get-config");
        node = lyd_new(data, ietfnc, "source");
        node = lyd_new_leaf(node, ietfnc, ncds2str[rpc_gc->source], NULL);
        if (!node) {
            lyd_free(data);
            return NC_MSG_ERROR;
        }
        if (rpc_gc->filter) {
            if (rpc_gc->filter[0] == '<') {
                node = lyd_new_anyxml(data, ietfnc, "filter", rpc_gc->filter);
                lyd_insert_attr(node, "type", "subtree");
            } else {
                node = lyd_new_anyxml(data, ietfnc, "filter", NULL);
                lyd_insert_attr(node, "type", "xpath");
                lyd_insert_attr(node, "select", rpc_gc->filter);
            }
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }

        if (rpc_gc->wd_mode) {
            if (!ietfncwd) {
                ietfncwd = ly_ctx_get_module(session->ctx, "ietf-netconf-with-defaults", NULL);
                if (!ietfncwd) {
                    ERR("Session %u: missing ietf-netconf-with-defaults schema in the context.", session->id);
                    return NC_MSG_ERROR;
                }
            }
            switch (rpc_gc->wd_mode) {
            case NC_WD_UNKNOWN:
                /* cannot get here */
                break;
            case NC_WD_ALL:
                node = lyd_new_leaf(data, ietfncwd, "with-defaults", "report-all");
                break;
            case NC_WD_ALL_TAG:
                node = lyd_new_leaf(data, ietfncwd, "with-defaults", "report-all-tagged");
                break;
            case NC_WD_TRIM:
                node = lyd_new_leaf(data, ietfncwd, "with-defaults", "trim");
                break;
            case NC_WD_EXPLICIT:
                node = lyd_new_leaf(data, ietfncwd, "with-defaults", "explicit");
                break;
            }
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }
        break;

    case NC_RPC_EDIT:
        rpc_e = (struct nc_rpc_edit *)rpc;

        data = lyd_new(NULL, ietfnc, "edit-config");
        node = lyd_new(data, ietfnc, "target");
        node = lyd_new_leaf(node, ietfnc, ncds2str[rpc_e->target], NULL);
        if (!node) {
            lyd_free(data);
            return NC_MSG_ERROR;
        }

        if (rpc_e->default_op) {
            node = lyd_new_leaf(data, ietfnc, "default-operation", rpcedit_dfltop2str[rpc_e->default_op]);
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }

        if (rpc_e->test_opt) {
            node = lyd_new_leaf(data, ietfnc, "test-option", rpcedit_testopt2str[rpc_e->test_opt]);
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }

        if (rpc_e->error_opt) {
            node = lyd_new_leaf(data, ietfnc, "error-option", rpcedit_erropt2str[rpc_e->error_opt]);
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }

        if (rpc_e->edit_cont[0] == '<') {
            node = lyd_new_anyxml(data, ietfnc, "config", rpc_e->edit_cont);
        } else {
            node = lyd_new_leaf(data, ietfnc, "url", rpc_e->edit_cont);
        }
        if (!node) {
            lyd_free(data);
            return NC_MSG_ERROR;
        }
        break;

    case NC_RPC_COPY:
        rpc_cp = (struct nc_rpc_copy *)rpc;

        data = lyd_new(NULL, ietfnc, "copy-config");
        node = lyd_new(data, ietfnc, "target");
        if (rpc_cp->url_trg) {
            node = lyd_new_leaf(node, ietfnc, "url", rpc_cp->url_trg);
        } else {
            node = lyd_new_leaf(node, ietfnc, ncds2str[rpc_cp->target], NULL);
        }
        if (!node) {
            lyd_free(data);
            return NC_MSG_ERROR;
        }

        node = lyd_new(data, ietfnc, "source");
        if (rpc_cp->url_config_src) {
            if (rpc_cp->url_config_src[0] == '<') {
                node = lyd_new_anyxml(node, ietfnc, "config", rpc_cp->url_config_src);
            } else {
                node = lyd_new_leaf(node, ietfnc, "url", rpc_cp->url_config_src);
            }
        } else {
            node = lyd_new_leaf(node, ietfnc, ncds2str[rpc_cp->source], NULL);
        }
        if (!node) {
            lyd_free(data);
            return NC_MSG_ERROR;
        }

        if (rpc_cp->wd_mode) {
            if (!ietfncwd) {
                ietfncwd = ly_ctx_get_module(session->ctx, "ietf-netconf-with-defaults", NULL);
                if (!ietfncwd) {
                    ERR("Session %u: missing ietf-netconf-with-defaults schema in the context.", session->id);
                    return NC_MSG_ERROR;
                }
            }
            switch (rpc_cp->wd_mode) {
            case NC_WD_UNKNOWN:
                /* cannot get here */
                break;
            case NC_WD_ALL:
                node = lyd_new_leaf(data, ietfncwd, "with-defaults", "report-all");
                break;
            case NC_WD_ALL_TAG:
                node = lyd_new_leaf(data, ietfncwd, "with-defaults", "report-all-tagged");
                break;
            case NC_WD_TRIM:
                node = lyd_new_leaf(data, ietfncwd, "with-defaults", "trim");
                break;
            case NC_WD_EXPLICIT:
                node = lyd_new_leaf(data, ietfncwd, "with-defaults", "explicit");
                break;
            }
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }
        break;

    case NC_RPC_DELETE:
        rpc_del = (struct nc_rpc_delete *)rpc;

        data = lyd_new(NULL, ietfnc, "delete-config");
        node = lyd_new(data, ietfnc, "target");
        if (rpc_del->url) {
            node = lyd_new_leaf(node, ietfnc, "url", rpc_del->url);
        } else {
            node = lyd_new_leaf(node, ietfnc, ncds2str[rpc_del->target], NULL);
        }
        if (!node) {
            lyd_free(data);
            return NC_MSG_ERROR;
        }
        break;

    case NC_RPC_LOCK:
        rpc_lock = (struct nc_rpc_lock *)rpc;

        data = lyd_new(NULL, ietfnc, "lock");
        node = lyd_new(data, ietfnc, "target");
        node = lyd_new_leaf(node, ietfnc, ncds2str[rpc_lock->target], NULL);
        if (!node) {
            lyd_free(data);
            return NC_MSG_ERROR;
        }
        break;

    case NC_RPC_UNLOCK:
        rpc_lock = (struct nc_rpc_lock *)rpc;

        data = lyd_new(NULL, ietfnc, "unlock");
        node = lyd_new(data, ietfnc, "target");
        node = lyd_new_leaf(node, ietfnc, ncds2str[rpc_lock->target], NULL);
        if (!node) {
            lyd_free(data);
            return NC_MSG_ERROR;
        }
        break;

    case NC_RPC_GET:
        rpc_g = (struct nc_rpc_get *)rpc;

        data = lyd_new(NULL, ietfnc, "get");
        if (rpc_g->filter) {
            if (rpc_g->filter[0] == '<') {
                node = lyd_new_anyxml(data, ietfnc, "filter", rpc_g->filter);
                lyd_insert_attr(node, "type", "subtree");
            } else {
                node = lyd_new_anyxml(data, ietfnc, "filter", NULL);
                lyd_insert_attr(node, "type", "xpath");
                lyd_insert_attr(node, "select", rpc_g->filter);
            }
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }

        if (rpc_g->wd_mode) {
            if (!ietfncwd) {
                ietfncwd = ly_ctx_get_module(session->ctx, "ietf-netconf-with-defaults", NULL);
                if (!ietfncwd) {
                    ERR("Session %u: missing ietf-netconf-with-defaults schema in the context.", session->id);
                    return NC_MSG_ERROR;
                }
            }
            switch (rpc_g->wd_mode) {
            case NC_WD_UNKNOWN:
                /* cannot get here */
                break;
            case NC_WD_ALL:
                node = lyd_new_leaf(data, ietfncwd, "with-defaults", "report-all");
                break;
            case NC_WD_ALL_TAG:
                node = lyd_new_leaf(data, ietfncwd, "with-defaults", "report-all-tagged");
                break;
            case NC_WD_TRIM:
                node = lyd_new_leaf(data, ietfncwd, "with-defaults", "trim");
                break;
            case NC_WD_EXPLICIT:
                node = lyd_new_leaf(data, ietfncwd, "with-defaults", "explicit");
                break;
            }
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }
        break;

    case NC_RPC_KILL:
        rpc_k = (struct nc_rpc_kill *)rpc;

        data = lyd_new(NULL, ietfnc, "kill-session");
        sprintf(str, "%u", rpc_k->sid);
        lyd_new_leaf(data, ietfnc, "session-id", str);
        break;

    case NC_RPC_COMMIT:
        rpc_com = (struct nc_rpc_commit *)rpc;

        data = lyd_new(NULL, ietfnc, "commit");
        if (rpc_com->confirmed) {
            lyd_new_leaf(data, ietfnc, "confirmed", NULL);
        }

        if (rpc_com->confirm_timeout) {
            sprintf(str, "%u", rpc_com->confirm_timeout);
            lyd_new_leaf(data, ietfnc, "confirm-timeout", str);
        }

        if (rpc_com->persist) {
            node = lyd_new_leaf(data, ietfnc, "persist", rpc_com->persist);
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }

        if (rpc_com->persist_id) {
            node = lyd_new_leaf(data, ietfnc, "persist-id", rpc_com->persist_id);
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }
        break;

    case NC_RPC_DISCARD:
        data = lyd_new(NULL, ietfnc, "discard-changes");
        break;

    case NC_RPC_CANCEL:
        rpc_can = (struct nc_rpc_cancel *)rpc;

        data = lyd_new(NULL, ietfnc, "cancel-commit");
        if (rpc_can->persist_id) {
            node = lyd_new_leaf(data, ietfnc, "persist-id", rpc_can->persist_id);
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }
        break;

    case NC_RPC_VALIDATE:
        rpc_val = (struct nc_rpc_validate *)rpc;

        data = lyd_new(NULL, ietfnc, "validate");
        node = lyd_new(data, ietfnc, "source");
        if (rpc_val->url_config_src) {
            if (rpc_val->url_config_src[0] == '<') {
                node = lyd_new_anyxml(node, ietfnc, "config", rpc_val->url_config_src);
            } else {
                node = lyd_new_leaf(node, ietfnc, "url", rpc_val->url_config_src);
            }
        } else {
            node = lyd_new_leaf(node, ietfnc, ncds2str[rpc_val->source], NULL);
        }
        if (!node) {
            lyd_free(data);
            return NC_MSG_ERROR;
        }
        break;

    case NC_RPC_GETSCHEMA:
        ietfncmon = ly_ctx_get_module(session->ctx, "ietf-netconf-monitoring", NULL);
        if (!ietfncmon) {
            ERR("Session %u: missing ietf-netconf-monitoring schema in the context.", session->id);
            return NC_MSG_ERROR;
        }

        rpc_gs = (struct nc_rpc_getschema *)rpc;

        data = lyd_new(NULL, ietfncmon, "get-schema");
        node = lyd_new_leaf(data, ietfncmon, "identifier", rpc_gs->identifier);
        if (!node) {
            lyd_free(data);
            return NC_MSG_ERROR;
        }
        if (rpc_gs->version) {
            node = lyd_new_leaf(data, ietfncmon, "version", rpc_gs->version);
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }
        if (rpc_gs->format) {
            node = lyd_new_leaf(data, ietfncmon, "format", rpc_gs->format);
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }
        break;

    case NC_RPC_SUBSCRIBE:
        notifs = ly_ctx_get_module(session->ctx, "notifications", NULL);
        if (!notifs) {
            ERR("Session %u: missing notifications schema in the context.", session->id);
            return NC_MSG_ERROR;
        }

        rpc_sub = (struct nc_rpc_subscribe *)rpc;

        data = lyd_new(NULL, notifs, "create-subscription");
        if (rpc_sub->stream) {
            node = lyd_new_leaf(data, notifs, "stream", rpc_sub->stream);
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }

        if (rpc_sub->filter) {
            if (rpc_sub->filter[0] == '<') {
                node = lyd_new_anyxml(data, notifs, "filter", rpc_sub->filter);
                lyd_insert_attr(node, "type", "subtree");
            } else {
                node = lyd_new_anyxml(data, notifs, "filter", NULL);
                lyd_insert_attr(node, "type", "xpath");
                lyd_insert_attr(node, "select", rpc_sub->filter);
            }
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }

        if (rpc_sub->start) {
            node = lyd_new_leaf(data, notifs, "startTime", rpc_sub->start);
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }

        if (rpc_sub->stop) {
            node = lyd_new_leaf(data, notifs, "stopTime", rpc_sub->stop);
            if (!node) {
                lyd_free(data);
                return NC_MSG_ERROR;
            }
        }
        break;
    default:
        ERRINT;
        return NC_MSG_ERROR;
    }

    if (lyd_validate(data, LYD_OPT_STRICT)) {
        lyd_free(data);
        return NC_MSG_ERROR;
    }

    ret = nc_timedlock(session->ti_lock, timeout, NULL);
    if (ret == -1) {
        /* error */
        r = NC_MSG_ERROR;
    } else if (!ret) {
        /* blocking */
        r = NC_MSG_WOULDBLOCK;
    } else {
        /* send RPC, store its message ID */
        r = nc_send_msg(session, data);
        cur_msgid = session->msgid;
    }
    pthread_mutex_unlock(session->ti_lock);

    lyd_free(data);

    if (r != NC_MSG_RPC) {
        return r;
    }

    *msgid = cur_msgid;
    return NC_MSG_RPC;
}