diff options
| -rw-r--r-- | net/mctp/route.c | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/net/mctp/route.c b/net/mctp/route.c index 04d29e910af9..b4ad47bb0da5 100644 --- a/net/mctp/route.c +++ b/net/mctp/route.c @@ -73,6 +73,40 @@ static struct mctp_sock *mctp_lookup_bind(struct net *net, struct sk_buff *skb) return NULL; } +/* A note on the key allocations. + * + * struct net->mctp.keys contains our set of currently-allocated keys for + * MCTP tag management. The lookup tuple for these is the peer EID, + * local EID and MCTP tag. + * + * In some cases, the peer EID may be MCTP_EID_ANY: for example, when a + * broadcast message is sent, we may receive responses from any peer EID. + * Because the broadcast dest address is equivalent to ANY, we create + * a key with (local = local-eid, peer = ANY). This allows a match on the + * incoming broadcast responses from any peer. + * + * We perform lookups when packets are received, and when tags are allocated + * in two scenarios: + * + * - when a packet is sent, with a locally-owned tag: we need to find an + * unused tag value for the (local, peer) EID pair. + * + * - when a tag is manually allocated: we need to find an unused tag value + * for the peer EID, but don't have a specific local EID at that stage. + * + * in the latter case, on successful allocation, we end up with a tag with + * (local = ANY, peer = peer-eid). + * + * So, the key set allows both a local EID of ANY, as well as a peer EID of + * ANY in the lookup tuple. Both may be ANY if we prealloc for a broadcast. + * The matching (in mctp_key_match()) during lookup allows the match value to + * be ANY in either the dest or source addresses. + * + * When allocating (+ inserting) a tag, we need to check for conflicts amongst + * the existing tag set. This requires macthing either exactly on the local + * and peer addresses, or either being ANY. + */ + static bool mctp_key_match(struct mctp_sk_key *key, mctp_eid_t local, mctp_eid_t peer, u8 tag) { @@ -368,6 +402,9 @@ static int mctp_route_input(struct mctp_route *route, struct sk_buff *skb) * key lookup to find the socket, but don't use this * key for reassembly - we'll create a more specific * one for future packets if required (ie, !EOM). + * + * this lookup requires key->peer to be MCTP_ADDR_ANY, + * it doesn't match just any key->peer. */ any_key = mctp_lookup_key(net, skb, MCTP_ADDR_ANY, &f); if (any_key) { |