• Eric Dumazet's avatar
    gro: fix different skb headrooms · 3d3be433
    Eric Dumazet authored
    Packets entering GRO might have different headrooms, even for a given
    flow (because of implementation details in drivers, like copybreak).
    We cant force drivers to deliver packets with a fixed headroom.
    
    1) fix skb_segment()
    
    skb_segment() makes the false assumption headrooms of fragments are same
    than the head. When CHECKSUM_PARTIAL is used, this can give csum_start
    errors, and crash later in skb_copy_and_csum_dev()
    
    2) allocate a minimal skb for head of frag_list
    
    skb_gro_receive() uses netdev_alloc_skb(headroom + skb_gro_offset(p)) to
    allocate a fresh skb. This adds NET_SKB_PAD to a padding already
    provided by netdevice, depending on various things, like copybreak.
    
    Use alloc_skb() to allocate an exact padding, to reduce cache line
    needs:
    NET_SKB_PAD + NET_IP_ALIGN
    
    bugzilla : https://bugzilla.kernel.org/show_bug.cgi?id=16626
    
    Many thanks to Plamen Petrov, testing many debugging patches !
    With help of Jarek Poplawski.
    Reported-by: default avatarPlamen Petrov <pvp-lsts@fs.uni-ruse.bg>
    Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
    CC: Jarek Poplawski <jarkao2@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    3d3be433
skbuff.c 75.3 KB