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    Subject[PATCH 3.8 070/121] net: ipv6: send pkttoobig immediately if orig frag size > mtu
    Date
    3.8.13.24 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Florian Westphal <fw@strlen.de>

    [ Upstream commit 418a31561d594a2b636c1e2fa94ecd9e1245abb1 ]

    If conntrack defragments incoming ipv6 frags it stores largest original
    frag size in ip6cb and sets ->local_df.

    We must thus first test the largest original frag size vs. mtu, and not
    vice versa.

    Without this patch PKTTOOBIG is still generated in ip6_fragment() later
    in the stack, but

    1) IPSTATS_MIB_INTOOBIGERRORS won't increment
    2) packet did (needlessly) traverse netfilter postrouting hook.

    Fixes: fe6cc55f3a9 ("net: ip, ipv6: handle gso skbs in forwarding path")
    Signed-off-by: Florian Westphal <fw@strlen.de>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    net/ipv6/ip6_output.c | 6 +++++-
    1 file changed, 5 insertions(+), 1 deletion(-)

    diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
    index 64809bd..41abcf7 100644
    --- a/net/ipv6/ip6_output.c
    +++ b/net/ipv6/ip6_output.c
    @@ -368,12 +368,16 @@ static inline int ip6_forward_finish(struct sk_buff *skb)

    static bool ip6_pkt_too_big(const struct sk_buff *skb, unsigned int mtu)
    {
    - if (skb->len <= mtu || skb->local_df)
    + if (skb->len <= mtu)
    return false;

    + /* ipv6 conntrack defrag sets max_frag_size + local_df */
    if (IP6CB(skb)->frag_max_size && IP6CB(skb)->frag_max_size > mtu)
    return true;

    + if (skb->local_df)
    + return false;
    +
    if (skb_is_gso(skb) && skb_gso_network_seglen(skb) <= mtu)
    return false;

    --
    1.9.1


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