• Herbert Xu's avatar
    [TCP]: Adjust {p,f}ackets_out correctly in tcp_retransmit_skb() · b5da623a
    Herbert Xu authored
    Well I've only found one potential cause for the assertion
    failure in tcp_mark_head_lost.  First of all, this can only
    occur if cnt > 1 since tp->packets_out is never zero here.
    If it did hit zero we'd have much bigger problems.
    
    So cnt is equal to fackets_out - reordering.  Normally
    fackets_out is less than packets_out.  The only reason
    I've found that might cause fackets_out to exceed packets_out
    is if tcp_fragment is called from tcp_retransmit_skb with a
    TSO skb and the current MSS is greater than the MSS stored
    in the TSO skb.  This might occur as the result of an expiring
    dst entry.
    
    In that case, packets_out may decrease (line 1380-1381 in
    tcp_output.c).  However, fackets_out is unchanged which means
    that it may in fact exceed packets_out.
    
    Previously tcp_retrans_try_collapse was the only place where
    packets_out can go down and it takes care of this by decrementing
    fackets_out.
    
    So we should make sure that fackets_out is reduced by an appropriate
    amount here as well.
    Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    b5da623a
tcp_output.c 58.8 KB