| Joe Hershberger | d22c338 | 2012-05-23 08:00:12 +0000 | [diff] [blame] | 1 | ------------------------------------------ |
| 2 | Link-local IP address auto-configuration |
| 3 | ------------------------------------------ |
| 4 | |
| 5 | Negotiate with other link-local clients on the local network |
| 6 | for an address that doesn't require explicit configuration. |
| 7 | This is especially useful if a DHCP server cannot be guaranteed |
| 8 | to exist in all environments that the device must operate. |
| 9 | |
| 10 | This is an implementation of RFC3927. |
| 11 | |
| 12 | ---------- |
| 13 | Commands |
| 14 | ---------- |
| 15 | |
| 16 | When CONFIG_CMD_LINK_LOCAL is defined in the board config file, |
| 17 | the "linklocal" command is available. This running this will |
| 18 | take approximately 5 seconds while the address is negotiated. |
| 19 | |
| 20 | ------------------------ |
| 21 | Environment interation |
| 22 | ------------------------ |
| 23 | |
| 24 | The "llipaddr" variable is set with the most recently |
| 25 | negotiated address and is preferred in future negotiations. |
| 26 | |
| 27 | The "ipaddr", "netmask", and "gatewayip" variables are set |
| 28 | after successful negotiation to enable network access. |
| 29 | |
| 30 | ------------- |
| 31 | Limitations |
| 32 | ------------- |
| 33 | |
| 34 | RFC3927 requires that addresses are continuously checked to |
| 35 | avoid conflicts, however this can only happen when the NetLoop |
| 36 | is getting called. It is possible for a conflict to go undetected |
| 37 | until a command that accesses the network is executed. |
| 38 | |
| 39 | Using NetConsole is one way to ensure that NetLoop is always |
| 40 | processing packets and monitoring for conflicts. |
| 41 | |
| 42 | This is also not a concern if the feature is use to connect |
| 43 | directly to another machine that may not be running a DHCP server. |
| 44 | |
| 45 | ---------------- |
| 46 | Example script |
| 47 | ---------------- |
| 48 | |
| 49 | This script allows use of DHCP and/or Link-local controlled |
| 50 | by env variables. It depends on CONFIG_CMD_LINK_LOCAL, CONFIG_CMD_DHCP, |
| 51 | and CONFIG_BOOTP_MAY_FAIL. |
| 52 | If both fail or are disabled, static settings are used. |
| 53 | |
| 54 | #define CONFIG_EXTRA_ENV_SETTINGS \ |
| 55 | "ipconfigcmd=if test \\\"$dhcpenabled\\\" -ne 0;" \ |
| 56 | "then " \ |
| 57 | "dhcpfail=0;dhcp || dhcpfail=1;" \ |
| 58 | "else " \ |
| 59 | "dhcpfail=-1;" \ |
| 60 | "fi;" \ |
| 61 | "if test \\\"$linklocalenabled\\\" -ne 0 -a " \ |
| 62 | "\\\"$dhcpfail\\\" -ne 0;" \ |
| 63 | "then " \ |
| 64 | "linklocal;" \ |
| 65 | "llfail=0;" \ |
| 66 | "else " \ |
| 67 | "llfail=-1;" \ |
| 68 | "fi;" \ |
| 69 | "if test \\\"$llfail\\\" -ne 0 -a " \ |
| 70 | "\\\"$dhcpfail\\\" -ne 0; " \ |
| 71 | "then " \ |
| 72 | "setenv ipaddr $sipaddr; " \ |
| 73 | "setenv netmask $snetmask; " \ |
| 74 | "setenv gatewayip $sgatewayip; " \ |
| 75 | "fi;\0" \ |