[PATCH v1 bpf-next 04/11] tcp: Don't initialise tp->tsoffset in tcp_get_cookie_sock().

[Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>]

When we create a full socket from SYN Cookie, we initialise
tcp_sk(sk)->tsoffset redundantly in tcp_get_cookie_sock() as
the field is inherited from tcp_rsk(req)->ts_off.

  cookie_v[46]_check
  | - treq->ts_off = 0 <------------------------- (0)
  ` - tcp_get_cookie_sock
      |- tcp_v[46]_syn_recv_sock
      |  `- tcp_create_openreq_child
      |	    `- newtp->tsoffset = treq->ts_off <-- (1)
      `- tcp_sk(child)->tsoffset = tsoff <------- (2)

Let's initialise tcp_rsk(req)->ts_off with the correct offset
and remove the second initialisation of tcp_sk(sk)->tsoffset.

Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
---
 include/net/tcp.h     | 2 +-
 net/ipv4/syncookies.c | 7 +++----
 net/ipv6/syncookies.c | 4 ++--
 3 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 91688d0dadcd..676618c89bb7 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -477,7 +477,7 @@ void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
 /* From syncookies.c */
 struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
 				 struct request_sock *req,
-				 struct dst_entry *dst, u32 tsoff);
+				 struct dst_entry *dst);
 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
 		      u32 cookie);
 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index b0cf6f4d66d8..514f1a4abdee 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -198,7 +198,7 @@ EXPORT_SYMBOL_GPL(__cookie_v4_check);
 
 struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
 				 struct request_sock *req,
-				 struct dst_entry *dst, u32 tsoff)
+				 struct dst_entry *dst)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	struct sock *child;
@@ -208,7 +208,6 @@ struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
 						 NULL, &own_req);
 	if (child) {
 		refcount_set(&req->rsk_refcnt, 1);
-		tcp_sk(child)->tsoffset = tsoff;
 		sock_rps_save_rxhash(child, skb);
 
 		if (rsk_drop_req(req)) {
@@ -378,7 +377,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	treq = tcp_rsk(req);
 	treq->rcv_isn		= ntohl(th->seq) - 1;
 	treq->snt_isn		= cookie;
-	treq->ts_off		= 0;
+	treq->ts_off		= tsoff;
 	treq->txhash		= net_tx_rndhash();
 	req->mss		= mss;
 	ireq->ir_num		= ntohs(th->dest);
@@ -441,7 +440,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	ireq->rcv_wscale  = rcv_wscale;
 	ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, net, &rt->dst);
 
-	ret = tcp_get_cookie_sock(sk, skb, req, &rt->dst, tsoff);
+	ret = tcp_get_cookie_sock(sk, skb, req, &rt->dst);
 	/* ip_queue_xmit() depends on our flow being setup
 	 * Normal sockets get it right from inet_csk_route_child_sock()
 	 */
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index b8ef6efbb60e..60bdc4d9150b 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -212,7 +212,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	treq->snt_synack	= 0;
 	treq->rcv_isn = ntohl(th->seq) - 1;
 	treq->snt_isn = cookie;
-	treq->ts_off = 0;
+	treq->ts_off = tsoff;
 	treq->txhash = net_tx_rndhash();
 	if (IS_ENABLED(CONFIG_SMC))
 		ireq->smc_ok = 0;
@@ -257,7 +257,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	ireq->rcv_wscale = rcv_wscale;
 	ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, net, dst);
 
-	ret = tcp_get_cookie_sock(sk, skb, req, dst, tsoff);
+	ret = tcp_get_cookie_sock(sk, skb, req, dst);
 out:
 	return ret;
 out_free:
-- 
2.30.2