From: Balazs Scheidler <bazsi@xxxxxxxxxx> 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@xxxxxxxxxx> Signed-off-by: KOVACS Krisztian <hidden@xxxxxxxxxx> --- include/net/netfilter/nf_tproxy_core.h | 6 ++- net/netfilter/nf_tproxy_core.c | 29 ++++++++++---- net/netfilter/xt_TPROXY.c | 68 ++++++++++++++++++++++++++++++-- net/netfilter/xt_socket.c | 2 - 4 files changed, 90 insertions(+), 15 deletions(-) diff --git a/include/net/netfilter/nf_tproxy_core.h b/include/net/netfilter/nf_tproxy_core.h index 208b46f..b3a8942 100644 --- a/include/net/netfilter/nf_tproxy_core.h +++ b/include/net/netfilter/nf_tproxy_core.h @@ -8,12 +8,16 @@ #include <net/inet_sock.h> #include <net/tcp.h> +#define NFT_LOOKUP_ANY 0 +#define NFT_LOOKUP_LISTENER 1 +#define NFT_LOOKUP_ESTABLISHED 2 + /* look up and get a reference to a matching socket */ extern struct sock * nf_tproxy_get_sock_v4(struct net *net, const u8 protocol, const __be32 saddr, const __be32 daddr, const __be16 sport, const __be16 dport, - const struct net_device *in, bool listening); + const struct net_device *in, int lookup_type); static inline void nf_tproxy_put_sock(struct sock *sk) diff --git a/net/netfilter/nf_tproxy_core.c b/net/netfilter/nf_tproxy_core.c index daab8c4..2ce945c 100644 --- a/net/netfilter/nf_tproxy_core.c +++ b/net/netfilter/nf_tproxy_core.c @@ -22,21 +22,34 @@ struct sock * nf_tproxy_get_sock_v4(struct net *net, const u8 protocol, const __be32 saddr, const __be32 daddr, const __be16 sport, const __be16 dport, - const struct net_device *in, bool listening_only) + const struct net_device *in, int lookup_type) { struct sock *sk; /* look up socket */ switch (protocol) { case IPPROTO_TCP: - if (listening_only) - sk = __inet_lookup_listener(net, &tcp_hashinfo, - daddr, ntohs(dport), - in->ifindex); - else + switch (lookup_type) { + case NFT_LOOKUP_ANY: sk = __inet_lookup(net, &tcp_hashinfo, saddr, sport, daddr, dport, in->ifindex); + break; + case NFT_LOOKUP_LISTENER: + sk = inet_lookup_listener(net, &tcp_hashinfo, + daddr, dport, + in->ifindex); + break; + case NFT_LOOKUP_ESTABLISHED: + sk = inet_lookup_established(net, &tcp_hashinfo, + saddr, sport, daddr, dport, + in->ifindex); + break; + default: + WARN_ON(1); + sk = NULL; + break; + } break; case IPPROTO_UDP: sk = udp4_lib_lookup(net, saddr, sport, daddr, dport, @@ -47,8 +60,8 @@ nf_tproxy_get_sock_v4(struct net *net, const u8 protocol, sk = NULL; } - pr_debug("tproxy socket lookup: proto %u %08x:%u -> %08x:%u, listener only: %d, sock %p\n", - protocol, ntohl(saddr), ntohs(sport), ntohl(daddr), ntohs(dport), listening_only, sk); + pr_debug("tproxy socket lookup: proto %u %08x:%u -> %08x:%u, lookup type: %d, sock %p\n", + protocol, ntohl(saddr), ntohs(sport), ntohl(daddr), ntohs(dport), lookup_type, sk); return sk; } diff --git a/net/netfilter/xt_TPROXY.c b/net/netfilter/xt_TPROXY.c index c61294d..67cbed8 100644 --- a/net/netfilter/xt_TPROXY.c +++ b/net/netfilter/xt_TPROXY.c @@ -24,6 +24,57 @@ #include <net/netfilter/ipv4/nf_defrag_ipv4.h> #include <net/netfilter/nf_tproxy_core.h> +/** + * 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)) { diff --git a/net/netfilter/xt_socket.c b/net/netfilter/xt_socket.c index 1ca8990..266faa0 100644 --- a/net/netfilter/xt_socket.c +++ b/net/netfilter/xt_socket.c @@ -142,7 +142,7 @@ socket_match(const struct sk_buff *skb, struct xt_action_param *par, #endif sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol, - saddr, daddr, sport, dport, par->in, false); + saddr, daddr, sport, dport, par->in, NFT_LOOKUP_ANY); if (sk != NULL) { bool wildcard; bool transparent = true; -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html