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77722b177a
It can happen, that tcp_retransmit_skb fails due to some error. In such cases we might end up into a state where tp->retrans_out is zero but that's only because we removed the TCPCB_SACKED_RETRANS bit from a segment but couldn't retransmit it because of the error that happened. Therefore some assumptions that retrans_out checks are based do not necessarily hold, as there still can be an old retransmission but that is only visible in TCPCB_EVER_RETRANS bit. As retransmission happen in sequential order (except for some very rare corner cases), it's enough to check the head skb for that bit. Main reason for all this complexity is the fact that connection dying time now depends on the validity of the retrans_stamp, in particular, that successive retransmissions of a segment must not advance retrans_stamp under any conditions. It seems after quick thinking that this has relatively low impact as eventually TCP will go into CA_Loss and either use the existing check for !retrans_stamp case or send a retransmission successfully, setting a new base time for the dying timer (can happen only once). At worst, the dying time will be approximately the double of the intented time. In addition, tcp_packet_delayed() will return wrong result (has some cc aspects but due to rarity of these errors, it's hardly an issue). One of retrans_stamp clearing happens indirectly through first going into CA_Open state and then a later ACK lets the clearing to happen. Thus tcp_try_keep_open has to be modified too. Thanks to Damian Lukowski <damian@tvk.rwth-aachen.de> for hinting that this possibility exists (though the particular case discussed didn't after all have it happening but was just a debug patch artifact). Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net> |
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