Current TCP code relies on the local port of the listening socket
being the same as the destination address of the incoming
connection. Port redirection used by many transparent proxying
techniques obviously breaks this, so we have to store the original
destination port address.
This patch extends struct inet_request_sock and stores the incoming
destination port value there. It also modifies the handshake code to
use that value as the source port when sending reply packets.
Signed-off-by: KOVACS Krisztian <hidden@xxxxxxxxxx>
---
include/net/inet_sock.h | 3 +++
include/net/tcp.h | 3 +++
net/ipv4/inet_connection_sock.c | 4 ++++
net/ipv4/syncookies.c | 3 +++
net/ipv4/tcp_output.c | 4 ++++
5 files changed, 17 insertions(+), 0 deletions(-)
diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
index e86832d..5339089 100644
--- a/include/net/inet_sock.h
+++ b/include/net/inet_sock.h
@@ -65,6 +65,9 @@ struct inet_request_sock {
#endif
__be32 loc_addr;
__be32 rmt_addr;
+#if defined(CONFIG_NETFILTER_TPROXY) || defined(CONFIG_NETFILTER_TPROXY_MODULE)
+ __be16 loc_port;
+#endif
__be16 rmt_port;
u16 snd_wscale : 4,
rcv_wscale : 4,
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 54053de..927d235 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -980,6 +980,9 @@ static inline void tcp_openreq_init(struct request_sock *req,
ireq->acked = 0;
ireq->ecn_ok = 0;
ireq->rmt_port = tcp_hdr(skb)->source;
+#if defined(CONFIG_NETFILTER_TPROXY) || defined(CONFIG_NETFILTER_TPROXY_MODULE)
+ ireq->loc_port = tcp_hdr(skb)->dest;
+#endif
}
extern void tcp_enter_memory_pressure(void);
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 26b9dbe..f47d966 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -502,6 +502,10 @@ struct sock *inet_csk_clone(struct sock *sk, const struct request_sock *req,
newicsk->icsk_bind_hash = NULL;
inet_sk(newsk)->dport = inet_rsk(req)->rmt_port;
+#if defined(CONFIG_IP_NF_TPROXY) || defined(CONFIG_IP_NF_TPROXY_MODULE)
+ inet_sk(newsk)->num = ntohs(inet_rsk(req)->loc_port);
+ inet_sk(newsk)->sport = inet_rsk(req)->loc_port;
+#endif
newsk->sk_write_space = sk_stream_write_space;
newicsk->icsk_retransmits = 0;
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index f7fad59..a55ccf1 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -223,6 +223,9 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
treq->rcv_isn = ntohl(th->seq) - 1;
treq->snt_isn = cookie;
req->mss = mss;
+#if defined(CONFIG_IP_NF_TPROXY) || defined(CONFIG_IP_NF_TPROXY_MODULE)
+ ireq->loc_port = th->dest;
+#endif
ireq->rmt_port = th->source;
ireq->loc_addr = ip_hdr(skb)->daddr;
ireq->rmt_addr = ip_hdr(skb)->saddr;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 666d8a5..69dd230 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2153,7 +2153,11 @@ struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst,
th->syn = 1;
th->ack = 1;
TCP_ECN_make_synack(req, th);
+#if defined(CONFIG_IP_NF_TPROXY) || defined(CONFIG_IP_NF_TPROXY_MODULE)
+ th->source = ireq->loc_port;
+#else
th->source = inet_sk(sk)->sport;
+#endif
th->dest = ireq->rmt_port;
TCP_SKB_CB(skb)->seq = tcp_rsk(req)->snt_isn;
TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1;
-
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