ip -- error messages

ip may fail for one of the following reasons:

• A syntax error on the command line: an unknown keyword, incorrectly formatted IP address et al. In this case ip prints an error message and exits. As a rule, the error message will contain information about the reason for the failure. Sometimes it also prints a help page.

• The arguments did not pass verification for self-consistency.

• ip failed to compile a kernel request from the arguments because the user didn't give enough information.

• The kernel returned an error to some syscall. In this case ip prints the error message, as it is output with perror(3), prefixed with a comment and a syscall identifier.

• The kernel returned an error to some RTNETLINK request. In this case ip prints the error message, as it is output with perror(3) prefixed with ``RTNETLINK answers:''.

All the operations are atomic, i.e. if the ip utility fails, it does not change anything in the system. One harmful exception is ip link command (Sec.4, p.), which may change only some of the device parameters given on command line.

It is difficult to list all the error messages (especially syntax errors). However, as a rule, their meaning is clear from the context of the command.

The most common mistakes are:

1. Netlink is not configured in the kernel. The message is:

   Cannot open netlink socket: Invalid value
   

2. RTNETLINK is not configured in the kernel. In this case one of the following messages may be printed, depending on the command:

   Cannot talk to rtnetlink: Connection refused
   Cannot send dump request: Connection refused
   

3. The CONFIG_IP_MULTIPLE_TABLES option was not selected when configuring the kernel. In this case any attempt to use the ip rule command will fail, f.e.

   kuznet@kaiser $ ip rule list
   RTNETLINK error: Invalid argument
   dump terminated