From 106e4c26b1529e559d1aae777f11b4f8f7bafc26 Mon Sep 17 00:00:00 2001 From: Balazs Scheidler Date: Thu, 21 Oct 2010 12:45:14 +0200 Subject: tproxy: kick out TIME_WAIT sockets in case a new connection comes in with the same tuple Without tproxy redirections an incoming SYN kicks out conflicting TIME_WAIT sockets, in order to handle clients that reuse ports within the TIME_WAIT period. The same mechanism didn't work in case TProxy is involved in finding the proper socket, as the time_wait processing code looked up the listening socket assuming that the listener addr/port matches those of the established connection. This is not the case with TProxy as the listener addr/port is possibly changed with the tproxy rule. Signed-off-by: Balazs Scheidler Signed-off-by: KOVACS Krisztian Signed-off-by: Patrick McHardy --- net/netfilter/xt_TPROXY.c | 68 +++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 63 insertions(+), 5 deletions(-) (limited to 'net/netfilter/xt_TPROXY.c') diff --git a/net/netfilter/xt_TPROXY.c b/net/netfilter/xt_TPROXY.c index 21bb2aff6b8f..e0b6900a92c1 100644 --- a/net/netfilter/xt_TPROXY.c +++ b/net/netfilter/xt_TPROXY.c @@ -24,6 +24,57 @@ #include #include +/** + * tproxy_handle_time_wait() - handle TCP TIME_WAIT reopen redirections + * @skb: The skb being processed. + * @par: Iptables target parameters. + * @sk: The TIME_WAIT TCP socket found by the lookup. + * + * We have to handle SYN packets arriving to TIME_WAIT sockets + * differently: instead of reopening the connection we should rather + * redirect the new connection to the proxy if there's a listener + * socket present. + * + * tproxy_handle_time_wait() consumes the socket reference passed in. + * + * Returns the listener socket if there's one, the TIME_WAIT socket if + * no such listener is found, or NULL if the TCP header is incomplete. + */ +static struct sock * +tproxy_handle_time_wait(struct sk_buff *skb, const struct xt_action_param *par, struct sock *sk) +{ + const struct iphdr *iph = ip_hdr(skb); + const struct xt_tproxy_target_info *tgi = par->targinfo; + struct tcphdr _hdr, *hp; + + hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr); + if (hp == NULL) { + inet_twsk_put(inet_twsk(sk)); + return NULL; + } + + if (hp->syn && !hp->rst && !hp->ack && !hp->fin) { + /* SYN to a TIME_WAIT socket, we'd rather redirect it + * to a listener socket if there's one */ + struct sock *sk2; + + sk2 = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, + iph->saddr, tgi->laddr ? tgi->laddr : iph->daddr, + hp->source, tgi->lport ? tgi->lport : hp->dest, + par->in, NFT_LOOKUP_LISTENER); + if (sk2) { + /* yeah, there's one, let's kill the TIME_WAIT + * socket and redirect to the listener + */ + inet_twsk_deschedule(inet_twsk(sk), &tcp_death_row); + inet_twsk_put(inet_twsk(sk)); + sk = sk2; + } + } + + return sk; +} + static unsigned int tproxy_tg(struct sk_buff *skb, const struct xt_action_param *par) { @@ -37,11 +88,18 @@ tproxy_tg(struct sk_buff *skb, const struct xt_action_param *par) return NF_DROP; sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, - iph->saddr, - tgi->laddr ? tgi->laddr : iph->daddr, - hp->source, - tgi->lport ? tgi->lport : hp->dest, - par->in, true); + iph->saddr, iph->daddr, + hp->source, hp->dest, + par->in, NFT_LOOKUP_ESTABLISHED); + + /* UDP has no TCP_TIME_WAIT state, so we never enter here */ + if (sk && sk->sk_state == TCP_TIME_WAIT) + sk = tproxy_handle_time_wait(skb, par, sk); + else if (!sk) + sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, + iph->saddr, tgi->laddr ? tgi->laddr : iph->daddr, + hp->source, tgi->lport ? tgi->lport : hp->dest, + par->in, NFT_LOOKUP_LISTENER); /* NOTE: assign_sock consumes our sk reference */ if (sk && nf_tproxy_assign_sock(skb, sk)) { -- cgit