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 <bazsi@balabit.hu> Signed-off-by: KOVACS Krisztian <hidden@balabit.hu> Signed-off-by: Patrick McHardy <kaber@trash.net>
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@ -8,12 +8,16 @@
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#include <net/inet_sock.h>
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#include <net/tcp.h>
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#define NFT_LOOKUP_ANY 0
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#define NFT_LOOKUP_LISTENER 1
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#define NFT_LOOKUP_ESTABLISHED 2
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/* look up and get a reference to a matching socket */
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extern struct sock *
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nf_tproxy_get_sock_v4(struct net *net, const u8 protocol,
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const __be32 saddr, const __be32 daddr,
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const __be16 sport, const __be16 dport,
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const struct net_device *in, bool listening);
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const struct net_device *in, int lookup_type);
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static inline void
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nf_tproxy_put_sock(struct sock *sk)
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@ -22,21 +22,34 @@ struct sock *
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nf_tproxy_get_sock_v4(struct net *net, const u8 protocol,
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const __be32 saddr, const __be32 daddr,
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const __be16 sport, const __be16 dport,
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const struct net_device *in, bool listening_only)
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const struct net_device *in, int lookup_type)
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{
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struct sock *sk;
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/* look up socket */
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switch (protocol) {
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case IPPROTO_TCP:
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if (listening_only)
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sk = __inet_lookup_listener(net, &tcp_hashinfo,
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daddr, ntohs(dport),
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in->ifindex);
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else
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switch (lookup_type) {
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case NFT_LOOKUP_ANY:
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sk = __inet_lookup(net, &tcp_hashinfo,
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saddr, sport, daddr, dport,
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in->ifindex);
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break;
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case NFT_LOOKUP_LISTENER:
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sk = inet_lookup_listener(net, &tcp_hashinfo,
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daddr, dport,
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in->ifindex);
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break;
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case NFT_LOOKUP_ESTABLISHED:
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sk = inet_lookup_established(net, &tcp_hashinfo,
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saddr, sport, daddr, dport,
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in->ifindex);
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break;
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default:
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WARN_ON(1);
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sk = NULL;
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break;
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}
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break;
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case IPPROTO_UDP:
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sk = udp4_lib_lookup(net, saddr, sport, daddr, dport,
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@ -47,8 +60,8 @@ nf_tproxy_get_sock_v4(struct net *net, const u8 protocol,
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sk = NULL;
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}
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pr_debug("tproxy socket lookup: proto %u %08x:%u -> %08x:%u, listener only: %d, sock %p\n",
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protocol, ntohl(saddr), ntohs(sport), ntohl(daddr), ntohs(dport), listening_only, sk);
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pr_debug("tproxy socket lookup: proto %u %08x:%u -> %08x:%u, lookup type: %d, sock %p\n",
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protocol, ntohl(saddr), ntohs(sport), ntohl(daddr), ntohs(dport), lookup_type, sk);
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return sk;
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}
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@ -24,6 +24,57 @@
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#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
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#include <net/netfilter/nf_tproxy_core.h>
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/**
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* tproxy_handle_time_wait() - handle TCP TIME_WAIT reopen redirections
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* @skb: The skb being processed.
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* @par: Iptables target parameters.
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* @sk: The TIME_WAIT TCP socket found by the lookup.
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*
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* We have to handle SYN packets arriving to TIME_WAIT sockets
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* differently: instead of reopening the connection we should rather
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* redirect the new connection to the proxy if there's a listener
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* socket present.
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*
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* tproxy_handle_time_wait() consumes the socket reference passed in.
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*
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* Returns the listener socket if there's one, the TIME_WAIT socket if
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* no such listener is found, or NULL if the TCP header is incomplete.
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*/
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static struct sock *
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tproxy_handle_time_wait(struct sk_buff *skb, const struct xt_action_param *par, struct sock *sk)
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{
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const struct iphdr *iph = ip_hdr(skb);
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const struct xt_tproxy_target_info *tgi = par->targinfo;
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struct tcphdr _hdr, *hp;
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hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
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if (hp == NULL) {
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inet_twsk_put(inet_twsk(sk));
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return NULL;
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}
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if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
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/* SYN to a TIME_WAIT socket, we'd rather redirect it
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* to a listener socket if there's one */
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struct sock *sk2;
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sk2 = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol,
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iph->saddr, tgi->laddr ? tgi->laddr : iph->daddr,
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hp->source, tgi->lport ? tgi->lport : hp->dest,
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par->in, NFT_LOOKUP_LISTENER);
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if (sk2) {
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/* yeah, there's one, let's kill the TIME_WAIT
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* socket and redirect to the listener
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*/
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inet_twsk_deschedule(inet_twsk(sk), &tcp_death_row);
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inet_twsk_put(inet_twsk(sk));
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sk = sk2;
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}
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}
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return sk;
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}
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static unsigned int
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tproxy_tg(struct sk_buff *skb, const struct xt_action_param *par)
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{
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return NF_DROP;
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sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol,
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iph->saddr,
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tgi->laddr ? tgi->laddr : iph->daddr,
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hp->source,
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tgi->lport ? tgi->lport : hp->dest,
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par->in, true);
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iph->saddr, iph->daddr,
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hp->source, hp->dest,
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par->in, NFT_LOOKUP_ESTABLISHED);
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/* UDP has no TCP_TIME_WAIT state, so we never enter here */
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if (sk && sk->sk_state == TCP_TIME_WAIT)
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sk = tproxy_handle_time_wait(skb, par, sk);
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else if (!sk)
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sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol,
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iph->saddr, tgi->laddr ? tgi->laddr : iph->daddr,
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hp->source, tgi->lport ? tgi->lport : hp->dest,
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par->in, NFT_LOOKUP_LISTENER);
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/* NOTE: assign_sock consumes our sk reference */
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if (sk && nf_tproxy_assign_sock(skb, sk)) {
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@ -142,7 +142,7 @@ socket_match(const struct sk_buff *skb, struct xt_action_param *par,
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#endif
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sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol,
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saddr, daddr, sport, dport, par->in, false);
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saddr, daddr, sport, dport, par->in, NFT_LOOKUP_ANY);
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if (sk != NULL) {
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bool wildcard;
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bool transparent = true;
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