netfilter: nf_conntrack: fix tcp_in_window for Fast Open
Currently the conntrack checks if the ending sequence of a packet falls within the observed receive window. However it does so even if it has not observe any packet from the remote yet and uses an uninitialized receive window (td_maxwin). If a connection uses Fast Open to send a SYN-data packet which is dropped afterward in the network. The subsequent SYNs retransmits will all fail this check and be discarded, leading to a connection timeout. This is because the SYN retransmit does not contain data payload so end == initial sequence number (isn) + 1 sender->td_end == isn + syn_data_len receiver->td_maxwin == 0 The fix is to only apply this check after td_maxwin is initialized. Reported-by: NMichael Chan <mcfchan@stanford.edu> Signed-off-by: NYuchung Cheng <ycheng@google.com> Acked-by: NEric Dumazet <edumazet@google.com> Acked-by: NJozsef Kadlecsik <kadlec@blackhole.kfki.hu> Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>
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