• Eric Dumazet's avatar
    tcp: take care of misalignments · 117632e6
    Eric Dumazet authored
    We discovered that TCP stack could retransmit misaligned skbs if a
    malicious peer acknowledged sub MSS frame. This currently can happen
    only if output interface is non SG enabled : If SG is enabled, tcp
    builds headless skbs (all payload is included in fragments), so the tcp
    trimming process only removes parts of skb fragments, header stay
    aligned.
    
    Some arches cant handle misalignments, so force a head reallocation and
    shrink headroom to MAX_TCP_HEADER.
    
    Dont care about misaligments on x86 and PPC (or other arches setting
    NET_IP_ALIGN to 0)
    
    This patch introduces __pskb_copy() which can specify the headroom of
    new head, and pskb_copy() becomes a wrapper on top of __pskb_copy()
    Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    117632e6
tcp_output.c 82.6 KB