[PATCH v1 net-next 0/8] tcp: Clean up and refactor cookie_v[46]_check().

[PATCH v1 net-next 0/8] tcp: Clean up and refactor cookie_v[46]_check().

[Kuniyuki Iwashima]

This is a preparation series for upcoming arbitrary SYN Cookie
support with BPF. [0]

There are slight differences between cookie_v[46]_check().  Such a
discrepancy caused an issue in the past, and BPF SYN Cookie support
will add more churn.

The primary purpose of this series is to clean up and refactor
cookie_v[46]_check() to minimise such discrepancies and make the
BPF series easier to review.

[0]: https://lore.kernel.org/netdev/20231121184245.69569-1-kuniyu@amazon.com/


Kuniyuki Iwashima (8):
  tcp: Clean up reverse xmas tree in cookie_v[46]_check().
  tcp: Cache sock_net(sk) in cookie_v[46]_check().
  tcp: Clean up goto labels in cookie_v[46]_check().
  tcp: Don't pass cookie to __cookie_v[46]_check().
  tcp: Don't initialise tp->tsoffset in tcp_get_cookie_sock().
  tcp: Move TCP-AO bits from cookie_v[46]_check() to tcp_ao_syncookie().
  tcp: Factorise cookie-independent fields initialisation in
    cookie_v[46]_check().
  tcp: Factorise cookie-dependent fields initialisation in
    cookie_v[46]_check()

 include/linux/netfilter_ipv6.h   |   8 +-
 include/net/tcp.h                |  22 ++--
 include/net/tcp_ao.h             |   6 +-
 net/core/filter.c                |  15 +--
 net/ipv4/syncookies.c            | 216 ++++++++++++++++---------------
 net/ipv4/tcp_ao.c                |  16 ++-
 net/ipv6/syncookies.c            | 108 +++++++---------
 net/netfilter/nf_synproxy_core.c |   4 +-
 8 files changed, 199 insertions(+), 196 deletions(-)

-- 
2.30.2

[PATCH v1 net-next 1/8] tcp: Clean up reverse xmas tree in cookie_v[46]_check().

[Kuniyuki Iwashima]

We will grow and cut the xmas tree in cookie_v[46]_check().
This patch cleans it up to make later patches tidy.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 net/ipv4/syncookies.c | 10 +++++-----
 net/ipv6/syncookies.c | 12 ++++++------
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index d37282c06e3d..a0118ea76734 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -331,18 +331,18 @@ EXPORT_SYMBOL_GPL(cookie_tcp_reqsk_alloc);
 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;
 	struct tcp_request_sock *treq;
-	struct tcp_sock *tp = tcp_sk(sk);
-	const struct tcphdr *th = tcp_hdr(skb);
-	__u32 cookie = ntohl(th->ack_seq) - 1;
-	struct sock *ret = sk;
 	struct request_sock *req;
+	struct sock *ret = sk;
 	int full_space, mss;
+	struct flowi4 fl4;
 	struct rtable *rt;
 	__u8 rcv_wscale;
-	struct flowi4 fl4;
 	u32 tsoff = 0;
 	int l3index;
 
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 12eedc6ca2cc..aa5fb5486cde 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -127,17 +127,17 @@ 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);
 	struct inet_request_sock *ireq;
 	struct tcp_request_sock *treq;
-	struct ipv6_pinfo *np = inet6_sk(sk);
-	struct tcp_sock *tp = tcp_sk(sk);
-	const struct tcphdr *th = tcp_hdr(skb);
-	__u32 cookie = ntohl(th->ack_seq) - 1;
-	struct sock *ret = sk;
 	struct request_sock *req;
-	int full_space, mss;
 	struct dst_entry *dst;
+	struct sock *ret = sk;
+	int full_space, mss;
 	__u8 rcv_wscale;
 	u32 tsoff = 0;
 	int l3index;
-- 
2.30.2

Re: [PATCH v1 net-next 1/8] tcp: Clean up reverse xmas tree in cookie_v[46]_check().

[Simon Horman]

On Wed, Nov 22, 2023 at 05:25:14PM -0800, Kuniyuki Iwashima wrote:
> We will grow and cut the xmas tree in cookie_v[46]_check().
> This patch cleans it up to make later patches tidy.
> 
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>

Reviewed-by: Simon Horman <horms@kernel.org>

[PATCH v1 net-next 2/8] tcp: Cache sock_net(sk) in cookie_v[46]_check().

[Kuniyuki Iwashima]

sock_net(sk) is used repeatedly in cookie_v[46]_check().
Let's cache it in a variable.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 net/ipv4/syncookies.c | 21 +++++++++++----------
 net/ipv6/syncookies.c | 19 ++++++++++---------
 2 files changed, 21 insertions(+), 19 deletions(-)

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index a0118ea76734..fb41bb18fe6b 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -336,6 +336,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	struct tcp_options_received tcp_opt;
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct inet_request_sock *ireq;
+	struct net *net = sock_net(sk);
 	struct tcp_request_sock *treq;
 	struct request_sock *req;
 	struct sock *ret = sk;
@@ -346,7 +347,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	u32 tsoff = 0;
 	int l3index;
 
-	if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_syncookies) ||
+	if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
 	    !th->ack || th->rst)
 		goto out;
 
@@ -355,24 +356,24 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 
 	mss = __cookie_v4_check(ip_hdr(skb), th, cookie);
 	if (mss == 0) {
-		__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
+		__NET_INC_STATS(net, LINUX_MIB_SYNCOOKIESFAILED);
 		goto out;
 	}
 
-	__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESRECV);
+	__NET_INC_STATS(net, LINUX_MIB_SYNCOOKIESRECV);
 
 	/* check for timestamp cookie support */
 	memset(&tcp_opt, 0, sizeof(tcp_opt));
-	tcp_parse_options(sock_net(sk), skb, &tcp_opt, 0, NULL);
+	tcp_parse_options(net, skb, &tcp_opt, 0, NULL);
 
 	if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) {
-		tsoff = secure_tcp_ts_off(sock_net(sk),
+		tsoff = secure_tcp_ts_off(net,
 					  ip_hdr(skb)->daddr,
 					  ip_hdr(skb)->saddr);
 		tcp_opt.rcv_tsecr -= tsoff;
 	}
 
-	if (!cookie_timestamp_decode(sock_net(sk), &tcp_opt))
+	if (!cookie_timestamp_decode(net, &tcp_opt))
 		goto out;
 
 	ret = NULL;
@@ -406,13 +407,13 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 
 	ireq->ir_iif = inet_request_bound_dev_if(sk, skb);
 
-	l3index = l3mdev_master_ifindex_by_index(sock_net(sk), ireq->ir_iif);
+	l3index = l3mdev_master_ifindex_by_index(net, ireq->ir_iif);
 	tcp_ao_syncookie(sk, skb, treq, AF_INET, l3index);
 
 	/* We throwed the options of the initial SYN away, so we hope
 	 * the ACK carries the same options again (see RFC1122 4.2.3.8)
 	 */
-	RCU_INIT_POINTER(ireq->ireq_opt, tcp_v4_save_options(sock_net(sk), skb));
+	RCU_INIT_POINTER(ireq->ireq_opt, tcp_v4_save_options(net, skb));
 
 	if (security_inet_conn_request(sk, skb, req)) {
 		reqsk_free(req);
@@ -433,7 +434,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 			   opt->srr ? opt->faddr : ireq->ir_rmt_addr,
 			   ireq->ir_loc_addr, th->source, th->dest, sk->sk_uid);
 	security_req_classify_flow(req, flowi4_to_flowi_common(&fl4));
-	rt = ip_route_output_key(sock_net(sk), &fl4);
+	rt = ip_route_output_key(net, &fl4);
 	if (IS_ERR(rt)) {
 		reqsk_free(req);
 		goto out;
@@ -453,7 +454,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 				  dst_metric(&rt->dst, RTAX_INITRWND));
 
 	ireq->rcv_wscale  = rcv_wscale;
-	ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, sock_net(sk), &rt->dst);
+	ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, net, &rt->dst);
 
 	ret = tcp_get_cookie_sock(sk, skb, req, &rt->dst, tsoff);
 	/* ip_queue_xmit() depends on our flow being setup
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index aa5fb5486cde..ba394fa73f41 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -133,6 +133,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	struct tcp_options_received tcp_opt;
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct inet_request_sock *ireq;
+	struct net *net = sock_net(sk);
 	struct tcp_request_sock *treq;
 	struct request_sock *req;
 	struct dst_entry *dst;
@@ -142,7 +143,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	u32 tsoff = 0;
 	int l3index;
 
-	if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_syncookies) ||
+	if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
 	    !th->ack || th->rst)
 		goto out;
 
@@ -151,24 +152,24 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 
 	mss = __cookie_v6_check(ipv6_hdr(skb), th, cookie);
 	if (mss == 0) {
-		__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
+		__NET_INC_STATS(net, LINUX_MIB_SYNCOOKIESFAILED);
 		goto out;
 	}
 
-	__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESRECV);
+	__NET_INC_STATS(net, LINUX_MIB_SYNCOOKIESRECV);
 
 	/* check for timestamp cookie support */
 	memset(&tcp_opt, 0, sizeof(tcp_opt));
-	tcp_parse_options(sock_net(sk), skb, &tcp_opt, 0, NULL);
+	tcp_parse_options(net, skb, &tcp_opt, 0, NULL);
 
 	if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) {
-		tsoff = secure_tcpv6_ts_off(sock_net(sk),
+		tsoff = secure_tcpv6_ts_off(net,
 					    ipv6_hdr(skb)->daddr.s6_addr32,
 					    ipv6_hdr(skb)->saddr.s6_addr32);
 		tcp_opt.rcv_tsecr -= tsoff;
 	}
 
-	if (!cookie_timestamp_decode(sock_net(sk), &tcp_opt))
+	if (!cookie_timestamp_decode(net, &tcp_opt))
 		goto out;
 
 	ret = NULL;
@@ -217,7 +218,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	treq->ts_off = 0;
 	treq->txhash = net_tx_rndhash();
 
-	l3index = l3mdev_master_ifindex_by_index(sock_net(sk), ireq->ir_iif);
+	l3index = l3mdev_master_ifindex_by_index(net, ireq->ir_iif);
 	tcp_ao_syncookie(sk, skb, treq, AF_INET6, l3index);
 
 	if (IS_ENABLED(CONFIG_SMC))
@@ -243,7 +244,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 		fl6.flowi6_uid = sk->sk_uid;
 		security_req_classify_flow(req, flowi6_to_flowi_common(&fl6));
 
-		dst = ip6_dst_lookup_flow(sock_net(sk), sk, &fl6, final_p);
+		dst = ip6_dst_lookup_flow(net, sk, &fl6, final_p);
 		if (IS_ERR(dst))
 			goto out_free;
 	}
@@ -261,7 +262,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 				  dst_metric(dst, RTAX_INITRWND));
 
 	ireq->rcv_wscale = rcv_wscale;
-	ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, sock_net(sk), dst);
+	ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, net, dst);
 
 	ret = tcp_get_cookie_sock(sk, skb, req, dst, tsoff);
 out:
-- 
2.30.2

Re: [PATCH v1 net-next 2/8] tcp: Cache sock_net(sk) in cookie_v[46]_check().

[Simon Horman]

On Wed, Nov 22, 2023 at 05:25:15PM -0800, Kuniyuki Iwashima wrote:
> sock_net(sk) is used repeatedly in cookie_v[46]_check().
> Let's cache it in a variable.
> 
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>

Reviewed-by: Simon Horman <horms@kernel.org>

[PATCH v1 net-next 3/8] tcp: Clean up goto labels in cookie_v[46]_check().

[Kuniyuki Iwashima]

We will support arbitrary SYN Cookie with BPF, and then reqsk
will be preallocated before cookie_v[46]_check().

Depending on how validation fails, we send RST or just drop skb.

To make the error handling easier, let's clean up goto labels.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 net/ipv4/syncookies.c | 22 +++++++++++-----------
 net/ipv6/syncookies.c |  4 ++--
 2 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index fb41bb18fe6b..8b7d7d7788af 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -376,11 +376,10 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	if (!cookie_timestamp_decode(net, &tcp_opt))
 		goto out;
 
-	ret = NULL;
 	req = cookie_tcp_reqsk_alloc(&tcp_request_sock_ops,
 				     &tcp_request_sock_ipv4_ops, sk, skb);
 	if (!req)
-		goto out;
+		goto out_drop;
 
 	ireq = inet_rsk(req);
 	treq = tcp_rsk(req);
@@ -415,10 +414,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	 */
 	RCU_INIT_POINTER(ireq->ireq_opt, tcp_v4_save_options(net, skb));
 
-	if (security_inet_conn_request(sk, skb, req)) {
-		reqsk_free(req);
-		goto out;
-	}
+	if (security_inet_conn_request(sk, skb, req))
+		goto out_free;
 
 	req->num_retrans = 0;
 
@@ -435,10 +432,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 			   ireq->ir_loc_addr, th->source, th->dest, sk->sk_uid);
 	security_req_classify_flow(req, flowi4_to_flowi_common(&fl4));
 	rt = ip_route_output_key(net, &fl4);
-	if (IS_ERR(rt)) {
-		reqsk_free(req);
-		goto out;
-	}
+	if (IS_ERR(rt))
+		goto out_free;
 
 	/* Try to redo what tcp_v4_send_synack did. */
 	req->rsk_window_clamp = tp->window_clamp ? :dst_metric(&rt->dst, RTAX_WINDOW);
@@ -462,5 +457,10 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	 */
 	if (ret)
 		inet_sk(ret)->cork.fl.u.ip4 = fl4;
-out:	return ret;
+out:
+	return ret;
+out_free:
+	reqsk_free(req);
+out_drop:
+	return NULL;
 }
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index ba394fa73f41..106376cbc9de 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -172,11 +172,10 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	if (!cookie_timestamp_decode(net, &tcp_opt))
 		goto out;
 
-	ret = NULL;
 	req = cookie_tcp_reqsk_alloc(&tcp6_request_sock_ops,
 				     &tcp_request_sock_ipv6_ops, sk, skb);
 	if (!req)
-		goto out;
+		goto out_drop;
 
 	ireq = inet_rsk(req);
 	treq = tcp_rsk(req);
@@ -269,5 +268,6 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	return ret;
 out_free:
 	reqsk_free(req);
+out_drop:
 	return NULL;
 }
-- 
2.30.2

Re: [PATCH v1 net-next 3/8] tcp: Clean up goto labels in cookie_v[46]_check().

[Simon Horman]

On Wed, Nov 22, 2023 at 05:25:16PM -0800, Kuniyuki Iwashima wrote:
> We will support arbitrary SYN Cookie with BPF, and then reqsk
> will be preallocated before cookie_v[46]_check().
> 
> Depending on how validation fails, we send RST or just drop skb.
> 
> To make the error handling easier, let's clean up goto labels.
> 
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>

Reviewed-by: Simon Horman <horms@kernel.org>

[PATCH v1 net-next 4/8] tcp: Don't pass cookie to __cookie_v[46]_check().

[Kuniyuki Iwashima]

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>
---
 include/linux/netfilter_ipv6.h   |  8 ++++----
 include/net/tcp.h                |  6 ++----
 net/core/filter.c                | 15 ++++-----------
 net/ipv4/syncookies.c            | 15 ++++++++-------
 net/ipv6/syncookies.c            | 15 ++++++++-------
 net/netfilter/nf_synproxy_core.c |  4 ++--
 6 files changed, 28 insertions(+), 35 deletions(-)

diff --git a/include/linux/netfilter_ipv6.h b/include/linux/netfilter_ipv6.h
index 7834c0be2831..61aa48f46dd7 100644
--- a/include/linux/netfilter_ipv6.h
+++ b/include/linux/netfilter_ipv6.h
@@ -51,7 +51,7 @@ struct nf_ipv6_ops {
 	u32 (*cookie_init_sequence)(const struct ipv6hdr *iph,
 				    const struct tcphdr *th, u16 *mssp);
 	int (*cookie_v6_check)(const struct ipv6hdr *iph,
-			       const struct tcphdr *th, __u32 cookie);
+			       const struct tcphdr *th);
 #endif
 	void (*route_input)(struct sk_buff *skb);
 	int (*fragment)(struct net *net, struct sock *sk, struct sk_buff *skb,
@@ -179,16 +179,16 @@ static inline u32 nf_ipv6_cookie_init_sequence(const struct ipv6hdr *iph,
 }
 
 static inline int nf_cookie_v6_check(const struct ipv6hdr *iph,
-				     const struct tcphdr *th, __u32 cookie)
+				     const struct tcphdr *th)
 {
 #if IS_ENABLED(CONFIG_SYN_COOKIES)
 #if IS_MODULE(CONFIG_IPV6)
 	const struct nf_ipv6_ops *v6_ops = nf_get_ipv6_ops();
 
 	if (v6_ops)
-		return v6_ops->cookie_v6_check(iph, th, cookie);
+		return v6_ops->cookie_v6_check(iph, th);
 #elif IS_BUILTIN(CONFIG_IPV6)
-	return __cookie_v6_check(iph, th, cookie);
+	return __cookie_v6_check(iph, th);
 #endif
 #endif
 	return 0;
diff --git a/include/net/tcp.h b/include/net/tcp.h
index d2f0736b76b8..2b2c79c7bbcd 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -491,8 +491,7 @@ void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
 struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
 				 struct request_sock *req,
 				 struct dst_entry *dst, u32 tsoff);
-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);
 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
 struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
 					    const struct tcp_request_sock_ops *af_ops,
@@ -586,8 +585,7 @@ bool cookie_ecn_ok(const struct tcp_options_received *opt,
 		   const struct net *net, const struct dst_entry *dst);
 
 /* From net/ipv6/syncookies.c */
-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);
 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
 
 u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
diff --git a/net/core/filter.c b/net/core/filter.c
index 383f96b0a1c7..d64baa7ac6cd 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -7229,7 +7229,6 @@ 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)))
@@ -7251,8 +7250,6 @@ 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).
 	 */
@@ -7261,7 +7258,7 @@ 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)
@@ -7272,7 +7269,7 @@ 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 */
 
@@ -7725,9 +7722,7 @@ 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;
@@ -7748,9 +7743,7 @@ 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;
-- 
2.30.2

Re: [PATCH v1 net-next 4/8] tcp: Don't pass cookie to __cookie_v[46]_check().

[Simon Horman]

On Wed, Nov 22, 2023 at 05:25:17PM -0800, Kuniyuki Iwashima wrote:
> 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>

[PATCH v1 net-next 5/8] tcp: Don't initialise tp->tsoffset in tcp_get_cookie_sock().

[Kuniyuki Iwashima]

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
  `- tcp_get_cookie_sock
     |- tcp_v[46]_syn_recv_sock
     |  `- tcp_create_openreq_child
     |	   `- newtp->tsoffset = treq->ts_off
     `- tcp_sk(child)->tsoffset = tsoff

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@amazon.com>
---
 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 2b2c79c7bbcd..cc7143a781da 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -490,7 +490,7 @@ 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);
 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
 struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index c08428d63d11..de051eb08db8 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -204,7 +204,7 @@ 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;
@@ -214,7 +214,6 @@ 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)) {
@@ -386,7 +385,7 @@ 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		= ntohl(th->ack_seq) - 1;
-	treq->ts_off		= 0;
+	treq->ts_off		= tsoff;
 	treq->txhash		= net_tx_rndhash();
 	req->mss		= mss;
 	ireq->ir_num		= ntohs(th->dest);
@@ -452,7 +451,7 @@ 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 4cd26c481168..18c2e3c1677b 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -215,7 +215,7 @@ 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 = ntohl(th->ack_seq) - 1;
-	treq->ts_off = 0;
+	treq->ts_off = tsoff;
 	treq->txhash = net_tx_rndhash();
 
 	l3index = l3mdev_master_ifindex_by_index(net, ireq->ir_iif);
@@ -264,7 +264,7 @@ 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

Re: [PATCH v1 net-next 5/8] tcp: Don't initialise tp->tsoffset in tcp_get_cookie_sock().

[Simon Horman]

On Wed, Nov 22, 2023 at 05:25:18PM -0800, Kuniyuki Iwashima wrote:
> 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
>   `- tcp_get_cookie_sock
>      |- tcp_v[46]_syn_recv_sock
>      |  `- tcp_create_openreq_child
>      |	   `- newtp->tsoffset = treq->ts_off
>      `- tcp_sk(child)->tsoffset = tsoff
> 
> 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@amazon.com>

Reviewed-by: Simon Horman <horms@kernel.org>

[PATCH v1 net-next 6/8] tcp: Move TCP-AO bits from cookie_v[46]_check() to tcp_ao_syncookie().

[Kuniyuki Iwashima]

We initialise treq->af_specific in cookie_tcp_reqsk_alloc() so that
we can look up a key later in tcp_create_openreq_child().

Initially, that change was added for MD5 by commit ba5a4fdd63ae ("tcp:
make sure treq->af_specific is initialized"), but it has not been used
since commit d0f2b7a9ca0a ("tcp: Disable header prediction for MD5
flow.").

Now, treq->af_specific is used only by TCP-AO, so, we can move that
initialisation into tcp_ao_syncookie().

In addition to that, l3index in cookie_v[46]_check() is only used for
tcp_ao_syncookie(), so let's move it as well.

While at it, we move down tcp_ao_syncookie() in cookie_v4_check() so
that it will be called after security_inet_conn_request() to make
functions order consistent with cookie_v6_check().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 include/net/tcp.h     |  1 -
 include/net/tcp_ao.h  |  6 ++----
 net/ipv4/syncookies.c | 16 ++++------------
 net/ipv4/tcp_ao.c     | 16 ++++++++++++++--
 net/ipv6/syncookies.c |  7 ++-----
 5 files changed, 22 insertions(+), 24 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index cc7143a781da..d4d0e9763175 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -494,7 +494,6 @@ struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th);
 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
 struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
-					    const struct tcp_request_sock_ops *af_ops,
 					    struct sock *sk, struct sk_buff *skb);
 #ifdef CONFIG_SYN_COOKIES
 
diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
index b56be10838f0..4d900ef8dfc3 100644
--- a/include/net/tcp_ao.h
+++ b/include/net/tcp_ao.h
@@ -265,8 +265,7 @@ void tcp_ao_established(struct sock *sk);
 void tcp_ao_finish_connect(struct sock *sk, struct sk_buff *skb);
 void tcp_ao_connect_init(struct sock *sk);
 void tcp_ao_syncookie(struct sock *sk, const struct sk_buff *skb,
-		      struct tcp_request_sock *treq,
-		      unsigned short int family, int l3index);
+		      struct request_sock *req, unsigned short int family);
 #else /* CONFIG_TCP_AO */
 
 static inline int tcp_ao_transmit_skb(struct sock *sk, struct sk_buff *skb,
@@ -277,8 +276,7 @@ static inline int tcp_ao_transmit_skb(struct sock *sk, struct sk_buff *skb,
 }
 
 static inline void tcp_ao_syncookie(struct sock *sk, const struct sk_buff *skb,
-				    struct tcp_request_sock *treq,
-				    unsigned short int family, int l3index)
+				    struct request_sock *req, unsigned short int family)
 {
 }
 
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index de051eb08db8..1e3783c97e28 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -286,9 +286,7 @@ bool cookie_ecn_ok(const struct tcp_options_received *tcp_opt,
 EXPORT_SYMBOL(cookie_ecn_ok);
 
 struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
-					    const struct tcp_request_sock_ops *af_ops,
-					    struct sock *sk,
-					    struct sk_buff *skb)
+					    struct sock *sk, struct sk_buff *skb)
 {
 	struct tcp_request_sock *treq;
 	struct request_sock *req;
@@ -303,9 +301,6 @@ struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
 
 	treq = tcp_rsk(req);
 
-	/* treq->af_specific might be used to perform TCP_MD5 lookup */
-	treq->af_specific = af_ops;
-
 	treq->syn_tos = TCP_SKB_CB(skb)->ip_dsfield;
 	treq->req_usec_ts = false;
 
@@ -345,7 +340,6 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	struct rtable *rt;
 	__u8 rcv_wscale;
 	u32 tsoff = 0;
-	int l3index;
 
 	if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
 	    !th->ack || th->rst)
@@ -376,8 +370,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	if (!cookie_timestamp_decode(net, &tcp_opt))
 		goto out;
 
-	req = cookie_tcp_reqsk_alloc(&tcp_request_sock_ops,
-				     &tcp_request_sock_ipv4_ops, sk, skb);
+	req = cookie_tcp_reqsk_alloc(&tcp_request_sock_ops, sk, skb);
 	if (!req)
 		goto out_drop;
 
@@ -406,9 +399,6 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 
 	ireq->ir_iif = inet_request_bound_dev_if(sk, skb);
 
-	l3index = l3mdev_master_ifindex_by_index(net, ireq->ir_iif);
-	tcp_ao_syncookie(sk, skb, treq, AF_INET, l3index);
-
 	/* We throwed the options of the initial SYN away, so we hope
 	 * the ACK carries the same options again (see RFC1122 4.2.3.8)
 	 */
@@ -417,6 +407,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	if (security_inet_conn_request(sk, skb, req))
 		goto out_free;
 
+	tcp_ao_syncookie(sk, skb, req, AF_INET);
+
 	req->num_retrans = 0;
 
 	/*
diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index 7696417d0640..c4cd1e09eb6b 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -844,18 +844,30 @@ static struct tcp_ao_key *tcp_ao_inbound_lookup(unsigned short int family,
 }
 
 void tcp_ao_syncookie(struct sock *sk, const struct sk_buff *skb,
-		      struct tcp_request_sock *treq,
-		      unsigned short int family, int l3index)
+		      struct request_sock *req, unsigned short int family)
 {
+	struct tcp_request_sock *treq = tcp_rsk(req);
 	const struct tcphdr *th = tcp_hdr(skb);
 	const struct tcp_ao_hdr *aoh;
 	struct tcp_ao_key *key;
+	int l3index;
+
+	/* treq->af_specific is used to perform TCP_AO lookup
+	 * in tcp_create_openreq_child().
+	 */
+#if IS_ENABLED(CONFIG_IPV6)
+	if (family == AF_INET6)
+		treq->af_specific = &tcp_request_sock_ipv6_ops;
+	else
+#endif
+		treq->af_specific = &tcp_request_sock_ipv4_ops;
 
 	treq->maclen = 0;
 
 	if (tcp_parse_auth_options(th, NULL, &aoh) || !aoh)
 		return;
 
+	l3index = l3mdev_master_ifindex_by_index(sock_net(sk), inet_rsk(req)->ir_iif);
 	key = tcp_ao_inbound_lookup(family, sk, skb, -1, aoh->keyid, l3index);
 	if (!key)
 		/* Key not found, continue without TCP-AO */
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 18c2e3c1677b..12b1809245f9 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -142,7 +142,6 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	int full_space, mss;
 	__u8 rcv_wscale;
 	u32 tsoff = 0;
-	int l3index;
 
 	if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
 	    !th->ack || th->rst)
@@ -173,8 +172,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	if (!cookie_timestamp_decode(net, &tcp_opt))
 		goto out;
 
-	req = cookie_tcp_reqsk_alloc(&tcp6_request_sock_ops,
-				     &tcp_request_sock_ipv6_ops, sk, skb);
+	req = cookie_tcp_reqsk_alloc(&tcp6_request_sock_ops, sk, skb);
 	if (!req)
 		goto out_drop;
 
@@ -218,8 +216,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	treq->ts_off = tsoff;
 	treq->txhash = net_tx_rndhash();
 
-	l3index = l3mdev_master_ifindex_by_index(net, ireq->ir_iif);
-	tcp_ao_syncookie(sk, skb, treq, AF_INET6, l3index);
+	tcp_ao_syncookie(sk, skb, req, AF_INET6);
 
 	if (IS_ENABLED(CONFIG_SMC))
 		ireq->smc_ok = 0;
-- 
2.30.2

Re: [PATCH v1 net-next 6/8] tcp: Move TCP-AO bits from cookie_v[46]_check() to tcp_ao_syncookie().

[Simon Horman]

On Wed, Nov 22, 2023 at 05:25:19PM -0800, Kuniyuki Iwashima wrote:
> We initialise treq->af_specific in cookie_tcp_reqsk_alloc() so that
> we can look up a key later in tcp_create_openreq_child().
> 
> Initially, that change was added for MD5 by commit ba5a4fdd63ae ("tcp:
> make sure treq->af_specific is initialized"), but it has not been used
> since commit d0f2b7a9ca0a ("tcp: Disable header prediction for MD5
> flow.").
> 
> Now, treq->af_specific is used only by TCP-AO, so, we can move that
> initialisation into tcp_ao_syncookie().
> 
> In addition to that, l3index in cookie_v[46]_check() is only used for
> tcp_ao_syncookie(), so let's move it as well.
> 
> While at it, we move down tcp_ao_syncookie() in cookie_v4_check() so
> that it will be called after security_inet_conn_request() to make
> functions order consistent with cookie_v6_check().
> 
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>

Reviewed-by: Simon Horman <horms@kernel.org>

[PATCH v1 net-next 7/8] tcp: Factorise cookie-independent fields initialisation in cookie_v[46]_check().

[Kuniyuki Iwashima]

We will support arbitrary SYN Cookie with BPF, and then some reqsk fields
are initialised in kfunc, and others are done in cookie_v[46]_check().

This patch factorises the common part as cookie_tcp_reqsk_init() and
calls it in cookie_tcp_reqsk_alloc() to minimise the discrepancy between
cookie_v[46]_check().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 net/ipv4/syncookies.c | 69 ++++++++++++++++++++++++-------------------
 net/ipv6/syncookies.c | 14 ---------
 2 files changed, 38 insertions(+), 45 deletions(-)

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 1e3783c97e28..9bca1c026525 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -285,10 +285,44 @@ bool cookie_ecn_ok(const struct tcp_options_received *tcp_opt,
 }
 EXPORT_SYMBOL(cookie_ecn_ok);
 
+static int cookie_tcp_reqsk_init(struct sock *sk, struct sk_buff *skb,
+				 struct request_sock *req)
+{
+	struct inet_request_sock *ireq = inet_rsk(req);
+	struct tcp_request_sock *treq = tcp_rsk(req);
+	const struct tcphdr *th = tcp_hdr(skb);
+
+	req->num_retrans = 0;
+
+	ireq->ir_num = ntohs(th->dest);
+	ireq->ir_rmt_port = th->source;
+	ireq->ir_iif = inet_request_bound_dev_if(sk, skb);
+	ireq->ir_mark = inet_request_mark(sk, skb);
+
+	if (IS_ENABLED(CONFIG_SMC))
+		ireq->smc_ok = 0;
+
+	treq->snt_synack = 0;
+	treq->tfo_listener = false;
+	treq->txhash = net_tx_rndhash();
+	treq->rcv_isn = ntohl(th->seq) - 1;
+	treq->snt_isn = ntohl(th->ack_seq) - 1;
+	treq->syn_tos = TCP_SKB_CB(skb)->ip_dsfield;
+	treq->syn_tos = TCP_SKB_CB(skb)->ip_dsfield;
+	treq->req_usec_ts = false;
+
+#if IS_ENABLED(CONFIG_MPTCP)
+	treq->is_mptcp = sk_is_mptcp(sk);
+	if (treq->is_mptcp)
+		return mptcp_subflow_init_cookie_req(req, sk, skb);
+#endif
+
+	return 0;
+}
+
 struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
 					    struct sock *sk, struct sk_buff *skb)
 {
-	struct tcp_request_sock *treq;
 	struct request_sock *req;
 
 	if (sk_is_mptcp(sk))
@@ -299,22 +333,10 @@ struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
 	if (!req)
 		return NULL;
 
-	treq = tcp_rsk(req);
-
-	treq->syn_tos = TCP_SKB_CB(skb)->ip_dsfield;
-	treq->req_usec_ts = false;
-
-#if IS_ENABLED(CONFIG_MPTCP)
-	treq->is_mptcp = sk_is_mptcp(sk);
-	if (treq->is_mptcp) {
-		int err = mptcp_subflow_init_cookie_req(req, sk, skb);
-
-		if (err) {
-			reqsk_free(req);
-			return NULL;
-		}
+	if (cookie_tcp_reqsk_init(sk, skb, req)) {
+		reqsk_free(req);
+		return NULL;
 	}
-#endif
 
 	return req;
 }
@@ -376,28 +398,15 @@ 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		= ntohl(th->ack_seq) - 1;
 	treq->ts_off		= tsoff;
-	treq->txhash		= net_tx_rndhash();
 	req->mss		= mss;
-	ireq->ir_num		= ntohs(th->dest);
-	ireq->ir_rmt_port	= th->source;
 	sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr);
 	sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr);
-	ireq->ir_mark		= inet_request_mark(sk, skb);
 	ireq->snd_wscale	= tcp_opt.snd_wscale;
 	ireq->sack_ok		= tcp_opt.sack_ok;
 	ireq->wscale_ok		= tcp_opt.wscale_ok;
 	ireq->tstamp_ok		= tcp_opt.saw_tstamp;
 	req->ts_recent		= tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
-	treq->snt_synack	= 0;
-	treq->tfo_listener	= false;
-
-	if (IS_ENABLED(CONFIG_SMC))
-		ireq->smc_ok = 0;
-
-	ireq->ir_iif = inet_request_bound_dev_if(sk, skb);
 
 	/* We throwed the options of the initial SYN away, so we hope
 	 * the ACK carries the same options again (see RFC1122 4.2.3.8)
@@ -409,8 +418,6 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 
 	tcp_ao_syncookie(sk, skb, req, AF_INET);
 
-	req->num_retrans = 0;
-
 	/*
 	 * We need to lookup the route here to get at the correct
 	 * window size. We should better make sure that the window size
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 12b1809245f9..e0a9220d1536 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -178,11 +178,8 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 
 	ireq = inet_rsk(req);
 	treq = tcp_rsk(req);
-	treq->tfo_listener = false;
 
 	req->mss = mss;
-	ireq->ir_rmt_port = th->source;
-	ireq->ir_num = ntohs(th->dest);
 	ireq->ir_v6_rmt_addr = ipv6_hdr(skb)->saddr;
 	ireq->ir_v6_loc_addr = ipv6_hdr(skb)->daddr;
 
@@ -196,31 +193,20 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 		ireq->pktopts = skb;
 	}
 
-	ireq->ir_iif = inet_request_bound_dev_if(sk, skb);
 	/* So that link locals have meaning */
 	if (!sk->sk_bound_dev_if &&
 	    ipv6_addr_type(&ireq->ir_v6_rmt_addr) & IPV6_ADDR_LINKLOCAL)
 		ireq->ir_iif = tcp_v6_iif(skb);
 
-	ireq->ir_mark = inet_request_mark(sk, skb);
-
-	req->num_retrans = 0;
 	ireq->snd_wscale	= tcp_opt.snd_wscale;
 	ireq->sack_ok		= tcp_opt.sack_ok;
 	ireq->wscale_ok		= tcp_opt.wscale_ok;
 	ireq->tstamp_ok		= tcp_opt.saw_tstamp;
 	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 = ntohl(th->ack_seq) - 1;
 	treq->ts_off = tsoff;
-	treq->txhash = net_tx_rndhash();
 
 	tcp_ao_syncookie(sk, skb, req, AF_INET6);
 
-	if (IS_ENABLED(CONFIG_SMC))
-		ireq->smc_ok = 0;
-
 	/*
 	 * We need to lookup the dst_entry to get the correct window size.
 	 * This is taken from tcp_v6_syn_recv_sock.  Somebody please enlighten
-- 
2.30.2

Re: [PATCH v1 net-next 7/8] tcp: Factorise cookie-independent fields initialisation in cookie_v[46]_check().

[Simon Horman]

On Wed, Nov 22, 2023 at 05:25:20PM -0800, Kuniyuki Iwashima wrote:
> We will support arbitrary SYN Cookie with BPF, and then some reqsk fields
> are initialised in kfunc, and others are done in cookie_v[46]_check().
> 
> This patch factorises the common part as cookie_tcp_reqsk_init() and
> calls it in cookie_tcp_reqsk_alloc() to minimise the discrepancy between
> cookie_v[46]_check().
> 
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> ---
>  net/ipv4/syncookies.c | 69 ++++++++++++++++++++++++-------------------
>  net/ipv6/syncookies.c | 14 ---------
>  2 files changed, 38 insertions(+), 45 deletions(-)
> 
> diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
> index 1e3783c97e28..9bca1c026525 100644
> --- a/net/ipv4/syncookies.c
> +++ b/net/ipv4/syncookies.c
> @@ -285,10 +285,44 @@ bool cookie_ecn_ok(const struct tcp_options_received *tcp_opt,
>  }
>  EXPORT_SYMBOL(cookie_ecn_ok);
>  
> +static int cookie_tcp_reqsk_init(struct sock *sk, struct sk_buff *skb,
> +				 struct request_sock *req)
> +{
> +	struct inet_request_sock *ireq = inet_rsk(req);
> +	struct tcp_request_sock *treq = tcp_rsk(req);
> +	const struct tcphdr *th = tcp_hdr(skb);
> +
> +	req->num_retrans = 0;
> +
> +	ireq->ir_num = ntohs(th->dest);
> +	ireq->ir_rmt_port = th->source;
> +	ireq->ir_iif = inet_request_bound_dev_if(sk, skb);
> +	ireq->ir_mark = inet_request_mark(sk, skb);
> +
> +	if (IS_ENABLED(CONFIG_SMC))
> +		ireq->smc_ok = 0;
> +
> +	treq->snt_synack = 0;
> +	treq->tfo_listener = false;
> +	treq->txhash = net_tx_rndhash();
> +	treq->rcv_isn = ntohl(th->seq) - 1;
> +	treq->snt_isn = ntohl(th->ack_seq) - 1;
> +	treq->syn_tos = TCP_SKB_CB(skb)->ip_dsfield;
> +	treq->syn_tos = TCP_SKB_CB(skb)->ip_dsfield;

Hi Iwashima-san,

The line above seems to be duplicated.

Other than that, this patch looks good to me.

Reviewed-by: Simon Horman <horms@kernel.org>


> +	treq->req_usec_ts = false;
> +
> +#if IS_ENABLED(CONFIG_MPTCP)
> +	treq->is_mptcp = sk_is_mptcp(sk);
> +	if (treq->is_mptcp)
> +		return mptcp_subflow_init_cookie_req(req, sk, skb);
> +#endif
> +
> +	return 0;
> +}

...

Re: [PATCH v1 net-next 7/8] tcp: Factorise cookie-independent fields initialisation in cookie_v[46]_check().

[Kuniyuki Iwashima]

From: Simon Horman <horms@kernel.org>
Date: Fri, 24 Nov 2023 21:44:18 +0000
> On Wed, Nov 22, 2023 at 05:25:20PM -0800, Kuniyuki Iwashima wrote:
> > We will support arbitrary SYN Cookie with BPF, and then some reqsk fields
> > are initialised in kfunc, and others are done in cookie_v[46]_check().
> > 
> > This patch factorises the common part as cookie_tcp_reqsk_init() and
> > calls it in cookie_tcp_reqsk_alloc() to minimise the discrepancy between
> > cookie_v[46]_check().
> > 
> > Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> > ---
> >  net/ipv4/syncookies.c | 69 ++++++++++++++++++++++++-------------------
> >  net/ipv6/syncookies.c | 14 ---------
> >  2 files changed, 38 insertions(+), 45 deletions(-)
> > 
> > diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
> > index 1e3783c97e28..9bca1c026525 100644
> > --- a/net/ipv4/syncookies.c
> > +++ b/net/ipv4/syncookies.c
> > @@ -285,10 +285,44 @@ bool cookie_ecn_ok(const struct tcp_options_received *tcp_opt,
> >  }
> >  EXPORT_SYMBOL(cookie_ecn_ok);
> >  
> > +static int cookie_tcp_reqsk_init(struct sock *sk, struct sk_buff *skb,
> > +				 struct request_sock *req)
> > +{
> > +	struct inet_request_sock *ireq = inet_rsk(req);
> > +	struct tcp_request_sock *treq = tcp_rsk(req);
> > +	const struct tcphdr *th = tcp_hdr(skb);
> > +
> > +	req->num_retrans = 0;
> > +
> > +	ireq->ir_num = ntohs(th->dest);
> > +	ireq->ir_rmt_port = th->source;
> > +	ireq->ir_iif = inet_request_bound_dev_if(sk, skb);
> > +	ireq->ir_mark = inet_request_mark(sk, skb);
> > +
> > +	if (IS_ENABLED(CONFIG_SMC))
> > +		ireq->smc_ok = 0;
> > +
> > +	treq->snt_synack = 0;
> > +	treq->tfo_listener = false;
> > +	treq->txhash = net_tx_rndhash();
> > +	treq->rcv_isn = ntohl(th->seq) - 1;
> > +	treq->snt_isn = ntohl(th->ack_seq) - 1;
> > +	treq->syn_tos = TCP_SKB_CB(skb)->ip_dsfield;
> > +	treq->syn_tos = TCP_SKB_CB(skb)->ip_dsfield;
> 
> Hi Iwashima-san,
> 
> The line above seems to be duplicated.

Ah good catch.
I'll fix it in v2.

Thanks for your review!

pw-bot: cr


> 
> Other than that, this patch looks good to me.
> 
> Reviewed-by: Simon Horman <horms@kernel.org>
> 
> 
> > +	treq->req_usec_ts = false;
> > +
> > +#if IS_ENABLED(CONFIG_MPTCP)
> > +	treq->is_mptcp = sk_is_mptcp(sk);
> > +	if (treq->is_mptcp)
> > +		return mptcp_subflow_init_cookie_req(req, sk, skb);
> > +#endif
> > +
> > +	return 0;
> > +}
> 

[PATCH v1 net-next 8/8] tcp: Factorise cookie-dependent fields initialisation in cookie_v[46]_check()

[Kuniyuki Iwashima]

We will support arbitrary SYN Cookie with BPF, and then kfunc at
TC will preallocate reqsk and initialise some fields that should
not be overwritten later by cookie_v[46]_check().

To simplify the flow in cookie_v[46]_check(), we move such fields'
initialisation to cookie_tcp_reqsk_alloc() and factorise non-BPF
SYN Cookie handling into cookie_tcp_check(), where we validate the
cookie and allocate reqsk, as done by kfunc later.

Note that we set ireq->ecn_ok in two steps, the latter of which will
be shared by the BPF case.  As cookie_ecn_ok() is one-liner, now
it's inlined.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 include/net/tcp.h     |  13 ++++--
 net/ipv4/syncookies.c | 106 +++++++++++++++++++++++-------------------
 net/ipv6/syncookies.c |  61 ++++++++++++------------
 3 files changed, 99 insertions(+), 81 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index d4d0e9763175..973555cb1d3f 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -494,7 +494,10 @@ struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th);
 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
 struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
-					    struct sock *sk, struct sk_buff *skb);
+					    struct sock *sk, struct sk_buff *skb,
+					    struct tcp_options_received *tcp_opt,
+					    int mss, u32 tsoff);
+
 #ifdef CONFIG_SYN_COOKIES
 
 /* Syncookies use a monotonic timer which increments every 60 seconds.
@@ -580,8 +583,12 @@ __u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);
 u64 cookie_init_timestamp(struct request_sock *req, u64 now);
 bool cookie_timestamp_decode(const struct net *net,
 			     struct tcp_options_received *opt);
-bool cookie_ecn_ok(const struct tcp_options_received *opt,
-		   const struct net *net, const struct dst_entry *dst);
+
+static inline bool cookie_ecn_ok(const struct net *net, const struct dst_entry *dst)
+{
+	return READ_ONCE(net->ipv4.sysctl_tcp_ecn) ||
+		dst_feature(dst, RTAX_FEATURE_ECN);
+}
 
 /* From net/ipv6/syncookies.c */
 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th);
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 9bca1c026525..beea4d05fafc 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -270,21 +270,6 @@ bool cookie_timestamp_decode(const struct net *net,
 }
 EXPORT_SYMBOL(cookie_timestamp_decode);
 
-bool cookie_ecn_ok(const struct tcp_options_received *tcp_opt,
-		   const struct net *net, const struct dst_entry *dst)
-{
-	bool ecn_ok = tcp_opt->rcv_tsecr & TS_OPT_ECN;
-
-	if (!ecn_ok)
-		return false;
-
-	if (READ_ONCE(net->ipv4.sysctl_tcp_ecn))
-		return true;
-
-	return dst_feature(dst, RTAX_FEATURE_ECN);
-}
-EXPORT_SYMBOL(cookie_ecn_ok);
-
 static int cookie_tcp_reqsk_init(struct sock *sk, struct sk_buff *skb,
 				 struct request_sock *req)
 {
@@ -321,8 +306,12 @@ static int cookie_tcp_reqsk_init(struct sock *sk, struct sk_buff *skb,
 }
 
 struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
-					    struct sock *sk, struct sk_buff *skb)
+					    struct sock *sk, struct sk_buff *skb,
+					    struct tcp_options_received *tcp_opt,
+					    int mss, u32 tsoff)
 {
+	struct inet_request_sock *ireq;
+	struct tcp_request_sock *treq;
 	struct request_sock *req;
 
 	if (sk_is_mptcp(sk))
@@ -338,40 +327,36 @@ struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
 		return NULL;
 	}
 
+	ireq = inet_rsk(req);
+	treq = tcp_rsk(req);
+
+	req->mss = mss;
+	req->ts_recent = tcp_opt->saw_tstamp ? tcp_opt->rcv_tsval : 0;
+
+	ireq->snd_wscale = tcp_opt->snd_wscale;
+	ireq->tstamp_ok = tcp_opt->saw_tstamp;
+	ireq->sack_ok = tcp_opt->sack_ok;
+	ireq->wscale_ok = tcp_opt->wscale_ok;
+	ireq->ecn_ok = tcp_opt->rcv_tsecr & TS_OPT_ECN;
+
+	treq->ts_off = tsoff;
+
 	return req;
 }
 EXPORT_SYMBOL_GPL(cookie_tcp_reqsk_alloc);
 
-/* On input, sk is a listener.
- * Output is listener if incoming packet would not create a child
- *           NULL if memory could not be allocated.
- */
-struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
+static struct request_sock *cookie_tcp_check(struct net *net, 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);
 	struct tcp_options_received tcp_opt;
-	struct tcp_sock *tp = tcp_sk(sk);
-	struct inet_request_sock *ireq;
-	struct net *net = sock_net(sk);
-	struct tcp_request_sock *treq;
-	struct request_sock *req;
-	struct sock *ret = sk;
-	int full_space, mss;
-	struct flowi4 fl4;
-	struct rtable *rt;
-	__u8 rcv_wscale;
 	u32 tsoff = 0;
-
-	if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
-	    !th->ack || th->rst)
-		goto out;
+	int mss;
 
 	if (tcp_synq_no_recent_overflow(sk))
 		goto out;
 
-	mss = __cookie_v4_check(ip_hdr(skb), th);
-	if (mss == 0) {
+	mss = __cookie_v4_check(ip_hdr(skb), tcp_hdr(skb));
+	if (!mss) {
 		__NET_INC_STATS(net, LINUX_MIB_SYNCOOKIESFAILED);
 		goto out;
 	}
@@ -392,21 +377,44 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	if (!cookie_timestamp_decode(net, &tcp_opt))
 		goto out;
 
-	req = cookie_tcp_reqsk_alloc(&tcp_request_sock_ops, sk, skb);
+	return cookie_tcp_reqsk_alloc(&tcp_request_sock_ops, sk, skb,
+				      &tcp_opt, mss, tsoff);
+out:
+	return ERR_PTR(-EINVAL);
+}
+
+/* On input, sk is a listener.
+ * Output is listener if incoming packet would not create a child
+ *           NULL if memory could not be allocated.
+ */
+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);
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct inet_request_sock *ireq;
+	struct net *net = sock_net(sk);
+	struct request_sock *req;
+	struct sock *ret = sk;
+	struct flowi4 fl4;
+	struct rtable *rt;
+	__u8 rcv_wscale;
+	int full_space;
+
+	if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
+	    !th->ack || th->rst)
+		goto out;
+
+	req = cookie_tcp_check(net, sk, skb);
+	if (IS_ERR(req))
+		goto out;
 	if (!req)
 		goto out_drop;
 
 	ireq = inet_rsk(req);
-	treq = tcp_rsk(req);
-	treq->ts_off		= tsoff;
-	req->mss		= mss;
+
 	sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr);
 	sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr);
-	ireq->snd_wscale	= tcp_opt.snd_wscale;
-	ireq->sack_ok		= tcp_opt.sack_ok;
-	ireq->wscale_ok		= tcp_opt.wscale_ok;
-	ireq->tstamp_ok		= tcp_opt.saw_tstamp;
-	req->ts_recent		= tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
 
 	/* We throwed the options of the initial SYN away, so we hope
 	 * the ACK carries the same options again (see RFC1122 4.2.3.8)
@@ -448,7 +456,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 				  dst_metric(&rt->dst, RTAX_INITRWND));
 
 	ireq->rcv_wscale  = rcv_wscale;
-	ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, net, &rt->dst);
+	ireq->ecn_ok &= cookie_ecn_ok(net, &rt->dst);
 
 	ret = tcp_get_cookie_sock(sk, skb, req, &rt->dst);
 	/* ip_queue_xmit() depends on our flow being setup
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index e0a9220d1536..c8d2ca27220c 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -127,31 +127,18 @@ int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th)
 }
 EXPORT_SYMBOL_GPL(__cookie_v6_check);
 
-struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
+static struct request_sock *cookie_tcp_check(struct net *net, struct sock *sk,
+					     struct sk_buff *skb)
 {
-	const struct tcphdr *th = tcp_hdr(skb);
-	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct tcp_options_received tcp_opt;
-	struct tcp_sock *tp = tcp_sk(sk);
-	struct inet_request_sock *ireq;
-	struct net *net = sock_net(sk);
-	struct tcp_request_sock *treq;
-	struct request_sock *req;
-	struct dst_entry *dst;
-	struct sock *ret = sk;
-	int full_space, mss;
-	__u8 rcv_wscale;
 	u32 tsoff = 0;
-
-	if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
-	    !th->ack || th->rst)
-		goto out;
+	int mss;
 
 	if (tcp_synq_no_recent_overflow(sk))
 		goto out;
 
-	mss = __cookie_v6_check(ipv6_hdr(skb), th);
-	if (mss == 0) {
+	mss = __cookie_v6_check(ipv6_hdr(skb), tcp_hdr(skb));
+	if (!mss) {
 		__NET_INC_STATS(net, LINUX_MIB_SYNCOOKIESFAILED);
 		goto out;
 	}
@@ -172,14 +159,37 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	if (!cookie_timestamp_decode(net, &tcp_opt))
 		goto out;
 
-	req = cookie_tcp_reqsk_alloc(&tcp6_request_sock_ops, sk, skb);
+	return cookie_tcp_reqsk_alloc(&tcp6_request_sock_ops, sk, skb,
+				      &tcp_opt, mss, tsoff);
+out:
+	return ERR_PTR(-EINVAL);
+}
+
+struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
+{
+	const struct tcphdr *th = tcp_hdr(skb);
+	struct ipv6_pinfo *np = inet6_sk(sk);
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct inet_request_sock *ireq;
+	struct net *net = sock_net(sk);
+	struct request_sock *req;
+	struct dst_entry *dst;
+	struct sock *ret = sk;
+	__u8 rcv_wscale;
+	int full_space;
+
+	if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
+	    !th->ack || th->rst)
+		goto out;
+
+	req = cookie_tcp_check(net, sk, skb);
+	if (IS_ERR(req))
+		goto out;
 	if (!req)
 		goto out_drop;
 
 	ireq = inet_rsk(req);
-	treq = tcp_rsk(req);
 
-	req->mss = mss;
 	ireq->ir_v6_rmt_addr = ipv6_hdr(skb)->saddr;
 	ireq->ir_v6_loc_addr = ipv6_hdr(skb)->daddr;
 
@@ -198,13 +208,6 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	    ipv6_addr_type(&ireq->ir_v6_rmt_addr) & IPV6_ADDR_LINKLOCAL)
 		ireq->ir_iif = tcp_v6_iif(skb);
 
-	ireq->snd_wscale	= tcp_opt.snd_wscale;
-	ireq->sack_ok		= tcp_opt.sack_ok;
-	ireq->wscale_ok		= tcp_opt.wscale_ok;
-	ireq->tstamp_ok		= tcp_opt.saw_tstamp;
-	req->ts_recent		= tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
-	treq->ts_off = tsoff;
-
 	tcp_ao_syncookie(sk, skb, req, AF_INET6);
 
 	/*
@@ -245,7 +248,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 				  dst_metric(dst, RTAX_INITRWND));
 
 	ireq->rcv_wscale = rcv_wscale;
-	ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, net, dst);
+	ireq->ecn_ok &= cookie_ecn_ok(net, dst);
 
 	ret = tcp_get_cookie_sock(sk, skb, req, dst);
 out:
-- 
2.30.2

Re: [PATCH v1 net-next 8/8] tcp: Factorise cookie-dependent fields initialisation in cookie_v[46]_check()

[Simon Horman]

On Wed, Nov 22, 2023 at 05:25:21PM -0800, Kuniyuki Iwashima wrote:
> We will support arbitrary SYN Cookie with BPF, and then kfunc at
> TC will preallocate reqsk and initialise some fields that should
> not be overwritten later by cookie_v[46]_check().
> 
> To simplify the flow in cookie_v[46]_check(), we move such fields'
> initialisation to cookie_tcp_reqsk_alloc() and factorise non-BPF
> SYN Cookie handling into cookie_tcp_check(), where we validate the
> cookie and allocate reqsk, as done by kfunc later.
> 
> Note that we set ireq->ecn_ok in two steps, the latter of which will
> be shared by the BPF case.  As cookie_ecn_ok() is one-liner, now
> it's inlined.
> 
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>

Reviewed-by: Simon Horman <horms@kernel.org>