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| author | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2010-10-11 22:35:40 +0400 |
|---|---|---|
| committer | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2010-10-12 08:57:40 +0400 |
| commit | 0b53d4604ac2b4f2faa9a62a04ea9b383ad2efe0 (patch) | |
| tree | 70ed0d136ef719f33655f78b31650d1c88cd3e00 /net/dccp/minisocks.c | |
| parent | 0ed8ddf4045fcfcac36bad753dc4046118c603ec (diff) | |
| download | linux-0b53d4604ac2b4f2faa9a62a04ea9b383ad2efe0.tar.xz | |
dccp: fix the adjustments to AWL and SWL
This fixes a problem and a potential loophole with regard to seqno/ackno
validity: currently the initial adjustments to AWL/SWL are only performed
once at the begin of the connection, during the handshake.
Since the Sequence Window feature is always greater than Wmin=32 (7.5.2),
it is however necessary to perform these adjustments at least for the first
W/W' (variables as per 7.5.1) packets in the lifetime of a connection.
This requirement is complicated by the fact that W/W' can change at any time
during the lifetime of a connection.
Therefore it is better to perform that safety check each time SWL/AWL are
updated, as implemented by the patch.
A second problem solved by this patch is that the remote/local Sequence Window
feature values (which set the bounds for AWL/SWL/SWH) are undefined until the
feature negotiation has completed.
During the initial handshake we have more stringent sequence number protection;
the changes added by this patch effect that {A,S}W{L,H} are within the correct
bounds at the instant that feature negotiation completes (since the SeqWin
feature activation handlers call dccp_update_gsr/gss()).
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Diffstat (limited to 'net/dccp/minisocks.c')
| -rw-r--r-- | net/dccp/minisocks.c | 30 |
1 files changed, 9 insertions, 21 deletions
diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c index 128b089d3aef..d7041a0963af 100644 --- a/net/dccp/minisocks.c +++ b/net/dccp/minisocks.c @@ -121,30 +121,18 @@ struct sock *dccp_create_openreq_child(struct sock *sk, * * Choose S.ISS (initial seqno) or set from Init Cookies * Initialize S.GAR := S.ISS - * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies - */ - newdp->dccps_gar = newdp->dccps_iss = dreq->dreq_iss; - dccp_update_gss(newsk, dreq->dreq_iss); - - newdp->dccps_isr = dreq->dreq_isr; - dccp_update_gsr(newsk, dreq->dreq_isr); - - /* - * SWL and AWL are initially adjusted so that they are not less than - * the initial Sequence Numbers received and sent, respectively: - * SWL := max(GSR + 1 - floor(W/4), ISR), - * AWL := max(GSS - W' + 1, ISS). - * These adjustments MUST be applied only at the beginning of the - * connection. + * Set S.ISR, S.GSR from packet (or Init Cookies) + * + * Setting AWL/AWH and SWL/SWH happens as part of the feature + * activation below, as these windows all depend on the local + * and remote Sequence Window feature values (7.5.2). */ - dccp_set_seqno(&newdp->dccps_swl, - max48(newdp->dccps_swl, newdp->dccps_isr)); - dccp_set_seqno(&newdp->dccps_awl, - max48(newdp->dccps_awl, newdp->dccps_iss)); + newdp->dccps_gss = newdp->dccps_iss = dreq->dreq_iss; + newdp->dccps_gar = newdp->dccps_iss; + newdp->dccps_gsr = newdp->dccps_isr = dreq->dreq_isr; /* - * Activate features after initialising the sequence numbers, - * since CCID initialisation may depend on GSS, ISR, ISS etc. + * Activate features: initialise CCIDs, sequence windows etc. */ if (dccp_feat_activate_values(newsk, &dreq->dreq_featneg)) { /* It is still raw copy of parent, so invalidate |