[RFC v2 mptcp-next 09/12] tcp: syncookies: create mptcp request socket for ACK cookies with MPTCP option

[Florian Westphal]

If SYN packet contains MP_CAPABLE option, keep it enabled.
Syncokie validation and cookie-based socket creation is changed to
instantiate an mptcp request sockets if the ACK contains an MPTCP
connection request.

Signed-off-by: Florian Westphal <f...@strlen.de>
---
 net/ipv4/syncookies.c | 21 +++++++++++++++++----
 net/ipv4/tcp_input.c  |  3 ---
 net/ipv6/syncookies.c | 17 ++++++++++++++---
 3 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index ee17f55401ef..5da49dc126f9 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -289,6 +289,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct 
sk_buff *skb)
        struct tcp_sock *tp = tcp_sk(sk);
        const struct tcphdr *th = tcp_hdr(skb);
        __u32 cookie = ntohl(th->ack_seq) - 1;
+       const struct request_sock_ops *ops;
        struct sock *ret = sk;
        struct request_sock *req;
        int mss;
@@ -326,12 +327,27 @@ struct sock *cookie_v4_check(struct sock *sk, struct 
sk_buff *skb)
                goto out;
 
        ret = NULL;
-       req = inet_reqsk_alloc(&tcp_request_sock_ops, sk, false); /* for safety 
*/
+       ops = &tcp_request_sock_ops;
+#ifdef CONFIG_MPTCP
+       if (sk_is_mptcp(sk))
+               ops = &mptcp_subflow_request_sock_ops;
+#endif
+
+       req = inet_reqsk_alloc(ops, sk, false); /* for safety */
        if (!req)
                goto out;
 
        ireq = inet_rsk(req);
        treq = tcp_rsk(req);
+       treq->is_mptcp = sk_is_mptcp(sk);
+
+       if (treq->is_mptcp) {
+               int err = mptcp_subflow_init_cookie_req(req, sk, skb);
+
+               if (err)
+                       goto out_free;
+       }
+
        treq->rcv_isn           = ntohl(th->seq) - 1;
        treq->snt_isn           = cookie;
        treq->ts_off            = 0;
@@ -350,9 +366,6 @@ struct sock *cookie_v4_check(struct sock *sk, struct 
sk_buff *skb)
        treq->snt_synack        = 0;
        treq->tfo_listener      = false;
 
-       if (IS_ENABLED(CONFIG_MPTCP))
-               treq->is_mptcp = 0;
-
        if (IS_ENABLED(CONFIG_SMC))
                ireq->smc_ok = 0;
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 17aa1c29d11c..7f4c21bca3b5 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6699,9 +6699,6 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 
        af_ops->init_req(req, sk, skb, want_cookie);
 
-       if (IS_ENABLED(CONFIG_MPTCP) && want_cookie)
-               tcp_rsk(req)->is_mptcp = 0;
-
        if (security_inet_conn_request(sk, skb, req))
                goto drop_and_free;
 
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 13235a012388..0a05c3c1e776 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -134,6 +134,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct 
sk_buff *skb)
        struct tcp_sock *tp = tcp_sk(sk);
        const struct tcphdr *th = tcp_hdr(skb);
        __u32 cookie = ntohl(th->ack_seq) - 1;
+       const struct request_sock_ops *ops;
        struct sock *ret = sk;
        struct request_sock *req;
        int mss;
@@ -170,7 +171,13 @@ struct sock *cookie_v6_check(struct sock *sk, struct 
sk_buff *skb)
                goto out;
 
        ret = NULL;
-       req = inet_reqsk_alloc(&tcp6_request_sock_ops, sk, false);
+       ops = &tcp6_request_sock_ops;
+#ifdef CONFIG_MPTCP
+       if (sk_is_mptcp(sk))
+               ops = &mptcp_subflow_request_sock_ops;
+#endif
+
+       req = inet_reqsk_alloc(ops, sk, false);
        if (!req)
                goto out;
 
@@ -178,8 +185,12 @@ struct sock *cookie_v6_check(struct sock *sk, struct 
sk_buff *skb)
        treq = tcp_rsk(req);
        treq->tfo_listener = false;
 
-       if (IS_ENABLED(CONFIG_MPTCP))
-               treq->is_mptcp = 0;
+       if (treq->is_mptcp) {
+               int err = mptcp_subflow_init_cookie_req(req, sk, skb);
+
+               if (err)
+                       goto out_free;
+       }
 
        if (security_inet_conn_request(sk, skb, req))
                goto out_free;
-- 
2.26.2