diff options
Diffstat (limited to 'Documentation/networking/tcp_ao.rst')
| -rw-r--r-- | Documentation/networking/tcp_ao.rst | 29 |
1 files changed, 19 insertions, 10 deletions
diff --git a/Documentation/networking/tcp_ao.rst b/Documentation/networking/tcp_ao.rst index 8a58321acce7..d5b6d0df63c3 100644 --- a/Documentation/networking/tcp_ao.rst +++ b/Documentation/networking/tcp_ao.rst @@ -9,7 +9,7 @@ segments between trusted peers. It adds a new TCP header option with a Message Authentication Code (MAC). MACs are produced from the content of a TCP segment using a hashing function with a password known to both peers. The intent of TCP-AO is to deprecate TCP-MD5 providing better security, -key rotation and support for variety of hashing algorithms. +key rotation and support for a variety of hashing algorithms. 1. Introduction =============== @@ -164,9 +164,9 @@ A: It should not, no action needs to be performed [7.5.2.e]:: is not available, no action is required (RNextKeyID of a received segment needs to match the MKT’s SendID). -Q: How current_key is set and when does it change? It is a user-triggered -change, or is it by a request from the remote peer? Is it set by the user -explicitly, or by a matching rule? +Q: How is current_key set, and when does it change? Is it a user-triggered +change, or is it triggered by a request from the remote peer? Is it set by the +user explicitly, or by a matching rule? A: current_key is set by RNextKeyID [6.1]:: @@ -233,8 +233,8 @@ always have one current_key [3.3]:: Q: Can a non-TCP-AO connection become a TCP-AO-enabled one? -A: No: for already established non-TCP-AO connection it would be impossible -to switch using TCP-AO as the traffic key generation requires the initial +A: No: for an already established non-TCP-AO connection it would be impossible +to switch to using TCP-AO, as the traffic key generation requires the initial sequence numbers. Paraphrasing, starting using TCP-AO would require re-establishing the TCP connection. @@ -292,7 +292,7 @@ no transparency is really needed and modern BGP daemons already have Linux provides a set of ``setsockopt()s`` and ``getsockopt()s`` that let userspace manage TCP-AO on a per-socket basis. In order to add/delete MKTs -``TCP_AO_ADD_KEY`` and ``TCP_AO_DEL_KEY`` TCP socket options must be used +``TCP_AO_ADD_KEY`` and ``TCP_AO_DEL_KEY`` TCP socket options must be used. It is not allowed to add a key on an established non-TCP-AO connection as well as to remove the last key from TCP-AO connection. @@ -337,6 +337,15 @@ TCP-AO per-socket counters are also duplicated with per-netns counters, exposed with SNMP. Those are ``TCPAOGood``, ``TCPAOBad``, ``TCPAOKeyNotFound``, ``TCPAORequired`` and ``TCPAODroppedIcmps``. +For monitoring purposes, there are following TCP-AO trace events: +``tcp_hash_bad_header``, ``tcp_hash_ao_required``, ``tcp_ao_handshake_failure``, +``tcp_ao_wrong_maclen``, ``tcp_ao_wrong_maclen``, ``tcp_ao_key_not_found``, +``tcp_ao_rnext_request``, ``tcp_ao_synack_no_key``, ``tcp_ao_snd_sne_update``, +``tcp_ao_rcv_sne_update``. It's possible to separately enable any of them and +one can filter them by net-namespace, 4-tuple, family, L3 index, and TCP header +flags. If a segment has a TCP-AO header, the filters may also include +keyid, rnext, and maclen. SNE updates include the rolled-over numbers. + RFC 5925 very permissively specifies how TCP port matching can be done for MKTs:: @@ -352,7 +361,7 @@ not implemented. 4. ``setsockopt()`` vs ``accept()`` race ======================================== -In contrast with TCP-MD5 established connection which has just one key, +In contrast with an established TCP-MD5 connection which has just one key, TCP-AO connections may have many keys, which means that accepted connections on a listen socket may have any amount of keys as well. As copying all those keys on a first properly signed SYN would make the request socket bigger, that @@ -365,7 +374,7 @@ keys from sockets that were already established, but not yet ``accept()``'ed, hanging in the accept queue. The reverse is valid as well: if userspace adds a new key for a peer on -a listener socket, the established sockets in accept queue won't +a listener socket, the established sockets in the accept queue won't have the new keys. At this moment, the resolution for the two races: @@ -373,7 +382,7 @@ At this moment, the resolution for the two races: and ``setsockopt(TCP_AO_DEL_KEY)`` vs ``accept()`` is delegated to userspace. This means that it's expected that userspace would check the MKTs on the socket that was returned by ``accept()`` to verify that any key rotation that -happened on listen socket is reflected on the newly established connection. +happened on the listen socket is reflected on the newly established connection. This is a similar "do-nothing" approach to TCP-MD5 from the kernel side and may be changed later by introducing new flags to ``tcp_ao_add`` |