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| -rw-r--r-- | doc/developer/vtysh.rst | 41 |
1 files changed, 40 insertions, 1 deletions
diff --git a/doc/developer/vtysh.rst b/doc/developer/vtysh.rst index 6506988a63..4a52eb0544 100644 --- a/doc/developer/vtysh.rst +++ b/doc/developer/vtysh.rst @@ -131,7 +131,7 @@ get the following:: ... Note that the static route doesn't show up there. Similarly, if we ask -*staticd* for its config, we get:: +*staticd* for its configuration, we get:: (config)# do sh running-config staticd @@ -160,3 +160,42 @@ This is because VTYSH asks each daemon for its currently running configuration, and combines equivalent blocks together. In the above example, it combined the ``vrf blue`` blocks from both *zebra* and *staticd* together into one. This is done in :file:`vtysh_config.c`. + +Protocol +======== + +VTYSH communicates with FRR daemons by way of domain socket. Each daemon +creates its own socket, typically in :file:`/var/run/frr/<daemon>.vty`. The +protocol is very simple. In the VTYSH to daemon direction, messages are simply +NULL-terminated strings, whose content are CLI commands. Here is a typical +message from VTYSH to a daemon: + +:: + + Request + + 00000000: 646f 2077 7269 7465 2074 6572 6d69 6e61 do write termina + 00000010: 6c0a 00 l.. + + +The response format has some more data in it. First is a NULL-terminated string +containing the plaintext response, which is just the output of the command that +was sent in the request. This is displayed to the user. The plaintext response +is followed by 3 null marker bytes, followed by a 1-byte status code that +indicates whether the command was successful or not. + +:: + + Response + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Plaintext Response | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Marker (0x00) | Status Code | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + +The first ``0x00`` byte in the marker also serves to terminate the plaintext +response. |