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>
Signed-off-by: Patrick McHardy <kaber@xxxxxxxxx>
---
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 5490fc3..8589e5e 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 21bb2af..e0b6900 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;
--
1.7.1
--
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