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Message-Id: <1493635640-24325-41-git-send-email-pablo@netfilter.org> Date: Mon, 1 May 2017 12:47:07 +0200 From: Pablo Neira Ayuso <pablo@...filter.org> To: netfilter-devel@...r.kernel.org Cc: davem@...emloft.net, netdev@...r.kernel.org Subject: [PATCH 40/53] netfilter: SYNPROXY: Return NF_STOLEN instead of NF_DROP during handshaking From: Gao Feng <fgao@...ai8.com> Current SYNPROXY codes return NF_DROP during normal TCP handshaking, it is not friendly to caller. Because the nf_hook_slow would treat the NF_DROP as an error, and return -EPERM. As a result, it may cause the top caller think it meets one error. For example, the following codes are from cfv_rx_poll() err = netif_receive_skb(skb); if (unlikely(err)) { ++cfv->ndev->stats.rx_dropped; } else { ++cfv->ndev->stats.rx_packets; cfv->ndev->stats.rx_bytes += skb_len; } When SYNPROXY returns NF_DROP, then netif_receive_skb returns -EPERM. As a result, the cfv driver would treat it as an error, and increase the rx_dropped counter. So use NF_STOLEN instead of NF_DROP now because there is no error happened indeed, and free the skb directly. Signed-off-by: Gao Feng <fgao@...ai8.com> Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org> --- net/ipv4/netfilter/ipt_SYNPROXY.c | 21 ++++++++++++++------- net/ipv6/netfilter/ip6t_SYNPROXY.c | 20 ++++++++++++++------ 2 files changed, 28 insertions(+), 13 deletions(-) diff --git a/net/ipv4/netfilter/ipt_SYNPROXY.c b/net/ipv4/netfilter/ipt_SYNPROXY.c index c308ee0ee0bc..af2b69b6895f 100644 --- a/net/ipv4/netfilter/ipt_SYNPROXY.c +++ b/net/ipv4/netfilter/ipt_SYNPROXY.c @@ -293,12 +293,16 @@ synproxy_tg4(struct sk_buff *skb, const struct xt_action_param *par) XT_SYNPROXY_OPT_ECN); synproxy_send_client_synack(net, skb, th, &opts); - return NF_DROP; - + consume_skb(skb); + return NF_STOLEN; } else if (th->ack && !(th->fin || th->rst || th->syn)) { /* ACK from client */ - synproxy_recv_client_ack(net, skb, th, &opts, ntohl(th->seq)); - return NF_DROP; + if (synproxy_recv_client_ack(net, skb, th, &opts, ntohl(th->seq))) { + consume_skb(skb); + return NF_STOLEN; + } else { + return NF_DROP; + } } return XT_CONTINUE; @@ -367,10 +371,13 @@ static unsigned int ipv4_synproxy_hook(void *priv, * number match the one of first SYN. */ if (synproxy_recv_client_ack(net, skb, th, &opts, - ntohl(th->seq) + 1)) + ntohl(th->seq) + 1)) { this_cpu_inc(snet->stats->cookie_retrans); - - return NF_DROP; + consume_skb(skb); + return NF_STOLEN; + } else { + return NF_DROP; + } } synproxy->isn = ntohl(th->ack_seq); diff --git a/net/ipv6/netfilter/ip6t_SYNPROXY.c b/net/ipv6/netfilter/ip6t_SYNPROXY.c index 1252537f215f..d3c4daa708b9 100644 --- a/net/ipv6/netfilter/ip6t_SYNPROXY.c +++ b/net/ipv6/netfilter/ip6t_SYNPROXY.c @@ -307,12 +307,17 @@ synproxy_tg6(struct sk_buff *skb, const struct xt_action_param *par) XT_SYNPROXY_OPT_ECN); synproxy_send_client_synack(net, skb, th, &opts); - return NF_DROP; + consume_skb(skb); + return NF_STOLEN; } else if (th->ack && !(th->fin || th->rst || th->syn)) { /* ACK from client */ - synproxy_recv_client_ack(net, skb, th, &opts, ntohl(th->seq)); - return NF_DROP; + if (synproxy_recv_client_ack(net, skb, th, &opts, ntohl(th->seq))) { + consume_skb(skb); + return NF_STOLEN; + } else { + return NF_DROP; + } } return XT_CONTINUE; @@ -388,10 +393,13 @@ static unsigned int ipv6_synproxy_hook(void *priv, * number match the one of first SYN. */ if (synproxy_recv_client_ack(net, skb, th, &opts, - ntohl(th->seq) + 1)) + ntohl(th->seq) + 1)) { this_cpu_inc(snet->stats->cookie_retrans); - - return NF_DROP; + consume_skb(skb); + return NF_STOLEN; + } else { + return NF_DROP; + } } synproxy->isn = ntohl(th->ack_seq); -- 2.1.4
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