tcp: Don't pass cookie to __cookie_v[46]_check().

tcp_hdr(skb) and SYN Cookie are passed to __cookie_v[46]_check(), but
none of the callers passes cookie other than ntohl(th->ack_seq) - 1.

Let's fetch it in __cookie_v[46]_check() instead of passing the cookie
over and over.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20231129022924.96156-5-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

4 files changed, 22 insertions, 27 deletions

diff --git a/net/core/filter.c b/net/core/filter.c
index 7e4d7c3bcc84..0adaa4afa35f 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -7238,7 +7238,6 @@ BPF_CALL_5(bpf_tcp_check_syncookie, struct sock *, sk, void *, iph, u32, iph_len
 	   struct tcphdr *, th, u32, th_len)
 {
 #ifdef CONFIG_SYN_COOKIES
-	u32 cookie;
 	int ret;
 
 	if (unlikely(!sk || th_len < sizeof(*th)))
@@ -7260,8 +7259,6 @@ BPF_CALL_5(bpf_tcp_check_syncookie, struct sock *, sk, void *, iph, u32, iph_len
 	if (tcp_synq_no_recent_overflow(sk))
 		return -ENOENT;
 
-	cookie = ntohl(th->ack_seq) - 1;
-
 	/* Both struct iphdr and struct ipv6hdr have the version field at the
 	 * same offset so we can cast to the shorter header (struct iphdr).
 	 */
@@ -7270,7 +7267,7 @@ BPF_CALL_5(bpf_tcp_check_syncookie, struct sock *, sk, void *, iph, u32, iph_len
 		if (sk->sk_family == AF_INET6 && ipv6_only_sock(sk))
 			return -EINVAL;
 
-		ret = __cookie_v4_check((struct iphdr *)iph, th, cookie);
+		ret = __cookie_v4_check((struct iphdr *)iph, th);
 		break;
 
 #if IS_BUILTIN(CONFIG_IPV6)
@@ -7281,7 +7278,7 @@ BPF_CALL_5(bpf_tcp_check_syncookie, struct sock *, sk, void *, iph, u32, iph_len
 		if (sk->sk_family != AF_INET6)
 			return -EINVAL;
 
-		ret = __cookie_v6_check((struct ipv6hdr *)iph, th, cookie);
+		ret = __cookie_v6_check((struct ipv6hdr *)iph, th);
 		break;
 #endif /* CONFIG_IPV6 */
 
@@ -7734,9 +7731,7 @@ static const struct bpf_func_proto bpf_tcp_raw_gen_syncookie_ipv6_proto = {
 BPF_CALL_2(bpf_tcp_raw_check_syncookie_ipv4, struct iphdr *, iph,
 	   struct tcphdr *, th)
 {
-	u32 cookie = ntohl(th->ack_seq) - 1;
-
-	if (__cookie_v4_check(iph, th, cookie) > 0)
+	if (__cookie_v4_check(iph, th) > 0)
 		return 0;
 
 	return -EACCES;
@@ -7757,9 +7752,7 @@ BPF_CALL_2(bpf_tcp_raw_check_syncookie_ipv6, struct ipv6hdr *, iph,
 	   struct tcphdr *, th)
 {
 #if IS_BUILTIN(CONFIG_IPV6)
-	u32 cookie = ntohl(th->ack_seq) - 1;
-
-	if (__cookie_v6_check(iph, th, cookie) > 0)
+	if (__cookie_v6_check(iph, th) > 0)
 		return 0;
 
 	return -EACCES;
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 8b7d7d7788af..c08428d63d11 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -189,12 +189,14 @@ __u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mssp)
  * Check if a ack sequence number is a valid syncookie.
  * Return the decoded mss if it is, or 0 if not.
  */
-int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
-		      u32 cookie)
+int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th)
 {
+	__u32 cookie = ntohl(th->ack_seq) - 1;
 	__u32 seq = ntohl(th->seq) - 1;
-	__u32 mssind = check_tcp_syn_cookie(cookie, iph->saddr, iph->daddr,
-					    th->source, th->dest, seq);
+	__u32 mssind;
+
+	mssind = check_tcp_syn_cookie(cookie, iph->saddr, iph->daddr,
+				      th->source, th->dest, seq);
 
 	return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0;
 }
@@ -332,7 +334,6 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 {
 	struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
 	const struct tcphdr *th = tcp_hdr(skb);
-	__u32 cookie = ntohl(th->ack_seq) - 1;
 	struct tcp_options_received tcp_opt;
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct inet_request_sock *ireq;
@@ -354,7 +355,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	if (tcp_synq_no_recent_overflow(sk))
 		goto out;
 
-	mss = __cookie_v4_check(ip_hdr(skb), th, cookie);
+	mss = __cookie_v4_check(ip_hdr(skb), th);
 	if (mss == 0) {
 		__NET_INC_STATS(net, LINUX_MIB_SYNCOOKIESFAILED);
 		goto out;
@@ -384,7 +385,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	ireq = inet_rsk(req);
 	treq = tcp_rsk(req);
 	treq->rcv_isn		= ntohl(th->seq) - 1;
-	treq->snt_isn		= cookie;
+	treq->snt_isn		= ntohl(th->ack_seq) - 1;
 	treq->ts_off		= 0;
 	treq->txhash		= net_tx_rndhash();
 	req->mss		= mss;
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 106376cbc9de..4cd26c481168 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -114,12 +114,14 @@ __u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mssp)
 	return __cookie_v6_init_sequence(iph, th, mssp);
 }
 
-int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
-		      __u32 cookie)
+int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th)
 {
+	__u32 cookie = ntohl(th->ack_seq) - 1;
 	__u32 seq = ntohl(th->seq) - 1;
-	__u32 mssind = check_tcp_syn_cookie(cookie, &iph->saddr, &iph->daddr,
-					    th->source, th->dest, seq);
+	__u32 mssind;
+
+	mssind = check_tcp_syn_cookie(cookie, &iph->saddr, &iph->daddr,
+				      th->source, th->dest, seq);
 
 	return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0;
 }
@@ -128,7 +130,6 @@ EXPORT_SYMBOL_GPL(__cookie_v6_check);
 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 {
 	const struct tcphdr *th = tcp_hdr(skb);
-	__u32 cookie = ntohl(th->ack_seq) - 1;
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct tcp_options_received tcp_opt;
 	struct tcp_sock *tp = tcp_sk(sk);
@@ -150,7 +151,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	if (tcp_synq_no_recent_overflow(sk))
 		goto out;
 
-	mss = __cookie_v6_check(ipv6_hdr(skb), th, cookie);
+	mss = __cookie_v6_check(ipv6_hdr(skb), th);
 	if (mss == 0) {
 		__NET_INC_STATS(net, LINUX_MIB_SYNCOOKIESFAILED);
 		goto out;
@@ -213,7 +214,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	req->ts_recent		= tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
 	treq->snt_synack	= 0;
 	treq->rcv_isn = ntohl(th->seq) - 1;
-	treq->snt_isn = cookie;
+	treq->snt_isn = ntohl(th->ack_seq) - 1;
 	treq->ts_off = 0;
 	treq->txhash = net_tx_rndhash();
 
diff --git a/net/netfilter/nf_synproxy_core.c b/net/netfilter/nf_synproxy_core.c
index 467671f2d42f..fbbc4fd37349 100644
--- a/net/netfilter/nf_synproxy_core.c
+++ b/net/netfilter/nf_synproxy_core.c
@@ -617,7 +617,7 @@ synproxy_recv_client_ack(struct net *net,
 	struct synproxy_net *snet = synproxy_pernet(net);
 	int mss;
 
-	mss = __cookie_v4_check(ip_hdr(skb), th, ntohl(th->ack_seq) - 1);
+	mss = __cookie_v4_check(ip_hdr(skb), th);
 	if (mss == 0) {
 		this_cpu_inc(snet->stats->cookie_invalid);
 		return false;
@@ -1034,7 +1034,7 @@ synproxy_recv_client_ack_ipv6(struct net *net,
 	struct synproxy_net *snet = synproxy_pernet(net);
 	int mss;
 
-	mss = nf_cookie_v6_check(ipv6_hdr(skb), th, ntohl(th->ack_seq) - 1);
+	mss = nf_cookie_v6_check(ipv6_hdr(skb), th);
 	if (mss == 0) {
 		this_cpu_inc(snet->stats->cookie_invalid);
 		return false;