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authorGerrit Renker <gerrit@erg.abdn.ac.uk>2008-11-12 00:48:44 -0800
committerDavid S. Miller <davem@davemloft.net>2008-11-12 00:48:44 -0800
commit9eca0a47dee201a73967026985b5f0a79a46bd36 (patch)
treebeb39fbd3c28865705d7409aa35fd59914257da9 /net/dccp/proto.c
parentd90ebcbfa7f5a8b4e20518c9f94c5c4e4cd3c2e5 (diff)
downloadlinux-2.6.38-lt-ux500-9eca0a47dee201a73967026985b5f0a79a46bd36.tar.gz
dccp: Resolve dependencies of features on choice of CCID
This provides a missing link in the code chain, as several features implicitly depend and/or rely on the choice of CCID. Most notably, this is the Send Ack Vector feature, but also Ack Ratio and Send Loss Event Rate (also taken care of). For Send Ack Vector, the situation is as follows: * since CCID2 mandates the use of Ack Vectors, there is no point in allowing endpoints which use CCID2 to disable Ack Vector features such a connection; * a peer with a TX CCID of CCID2 will always expect Ack Vectors, and a peer with a RX CCID of CCID2 must always send Ack Vectors (RFC 4341, sec. 4); * for all other CCIDs, the use of (Send) Ack Vector is optional and thus negotiable. However, this implies that the code negotiating the use of Ack Vectors also supports it (i.e. is able to supply and to either parse or ignore received Ack Vectors). Since this is not the case (CCID-3 has no Ack Vector support), the use of Ack Vectors is here disabled, with a comment in the source code. An analogous consideration arises for the Send Loss Event Rate feature, since the CCID-3 implementation does not support the loss interval options of RFC 4342. To make such use explicit, corresponding feature-negotiation options are inserted which signal the use of the loss event rate option, as it is used by the CCID3 code. Lastly, the values of the Ack Ratio feature are matched to the choice of CCID. The patch implements this as a function which is called after the user has made all other registrations for changing default values of features. The table is variable-length, the reserved (and hence for feature-negotiation invalid, confirmed by considering section 19.4 of RFC 4340) feature number `0' is used to mark the end of the table. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/dccp/proto.c')
-rw-r--r--net/dccp/proto.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index b4b10cbd888..46cb3490d48 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -278,6 +278,9 @@ static inline int dccp_listen_start(struct sock *sk, int backlog)
struct dccp_sock *dp = dccp_sk(sk);
dp->dccps_role = DCCP_ROLE_LISTEN;
+ /* do not start to listen if feature negotiation setup fails */
+ if (dccp_feat_finalise_settings(dp))
+ return -EPROTO;
return inet_csk_listen_start(sk, backlog);
}