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    Subject[PATCH 3.4 140/146] bridge: superfluous skb->nfct check in br_nf_dev_queue_xmit
    Date
    From: Vasily Averin <vvs@parallels.com>

    3.4.109-rc1 review patch. If anyone has any objections, please let me know.

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


    commit aff09ce303f83bd370772349238482ae422a2341 upstream.

    Currently bridge can silently drop ipv4 fragments.
    If node have loaded nf_defrag_ipv4 module but have no nf_conntrack_ipv4,
    br_nf_pre_routing defragments incoming ipv4 fragments
    but nfct check in br_nf_dev_queue_xmit does not allow re-fragment combined
    packet back, and therefore it is dropped in br_dev_queue_push_xmit without
    incrementing of any failcounters

    It seems the only way to hit the ip_fragment code in the bridge xmit
    path is to have a fragment list whose reassembled fragments go over
    the mtu. This only happens if nf_defrag is enabled. Thanks to
    Florian Westphal for providing feedback to clarify this.

    Defragmentation ipv4 is required not only in conntracks but at least in
    TPROXY target and socket match, therefore #ifdef is changed from
    NF_CONNTRACK_IPV4 to NF_DEFRAG_IPV4

    Signed-off-by: Vasily Averin <vvs@openvz.org>
    Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
    Cc: Kirill Tkhai <ktkhai@odin.com>
    Signed-off-by: Zefan Li <lizefan@huawei.com>
    ---
    net/bridge/br_netfilter.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
    index e54ef82..5ba4248 100644
    --- a/net/bridge/br_netfilter.c
    +++ b/net/bridge/br_netfilter.c
    @@ -818,12 +818,12 @@ static unsigned int br_nf_forward_arp(unsigned int hook, struct sk_buff *skb,
    return NF_STOLEN;
    }

    -#if IS_ENABLED(CONFIG_NF_CONNTRACK_IPV4)
    +#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4)
    static int br_nf_dev_queue_xmit(struct sk_buff *skb)
    {
    int ret;

    - if (skb->nfct != NULL && skb->protocol == htons(ETH_P_IP) &&
    + if (skb->protocol == htons(ETH_P_IP) &&
    skb->len + nf_bridge_mtu_reduction(skb) > skb->dev->mtu &&
    !skb_is_gso(skb)) {
    if (br_parse_ip_options(skb))
    --
    1.9.1


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