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Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/networking/mctp.rst | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/Documentation/networking/mctp.rst b/Documentation/networking/mctp.rst index fa7730dbf7b9..46f74bffce0f 100644 --- a/Documentation/networking/mctp.rst +++ b/Documentation/networking/mctp.rst @@ -211,3 +211,62 @@ remote address is already known, or the message does not require a reply. Like the send calls, sockets will only receive responses to requests they have sent (TO=1) and may only respond (TO=0) to requests they have received. + +Kernel internals +================ + +There are a few possible packet flows in the MCTP stack: + +1. local TX to remote endpoint, message <= MTU:: + + sendmsg() + -> mctp_local_output() + : route lookup + -> rt->output() (== mctp_route_output) + -> dev_queue_xmit() + +2. local TX to remote endpoint, message > MTU:: + + sendmsg() + -> mctp_local_output() + -> mctp_do_fragment_route() + : creates packet-sized skbs. For each new skb: + -> rt->output() (== mctp_route_output) + -> dev_queue_xmit() + +3. remote TX to local endpoint, single-packet message:: + + mctp_pkttype_receive() + : route lookup + -> rt->output() (== mctp_route_input) + : sk_key lookup + -> sock_queue_rcv_skb() + +4. remote TX to local endpoint, multiple-packet message:: + + mctp_pkttype_receive() + : route lookup + -> rt->output() (== mctp_route_input) + : sk_key lookup + : stores skb in struct sk_key->reasm_head + + mctp_pkttype_receive() + : route lookup + -> rt->output() (== mctp_route_input) + : sk_key lookup + : finds existing reassembly in sk_key->reasm_head + : appends new fragment + -> sock_queue_rcv_skb() + +Key refcounts +------------- + + * keys are refed by: + + - a skb: during route output, stored in ``skb->cb``. + + - netns and sock lists. + + * keys can be associated with a device, in which case they hold a + reference to the dev (set through ``key->dev``, counted through + ``dev->key_count``). Multiple keys can reference the device. |