tcp: merge 'init_req' and 'route_req' functions

The Multipath-TCP standard (RFC 8684) says that an MPTCP host should send
a TCP reset if the token in a MP_JOIN request is unknown.

At this time we don't do this, the 3whs completes and the 'new subflow'
is reset afterwards.  There are two ways to allow MPTCP to send the
reset.

1. override 'send_synack' callback and emit the rst from there.
   The drawback is that the request socket gets inserted into the
   listeners queue just to get removed again right away.

2. Send the reset from the 'route_req' function instead.
   This avoids the 'add&remove request socket', but route_req lacks the
   skb that is required to send the TCP reset.

Instead of just adding the skb to that function for MPTCP sake alone,
Paolo suggested to merge init_req and route_req functions.

This saves one indirection from syn processing path and provides the skb
to the merged function at the same time.

'send reset on unknown mptcp join token' is added in next patch.

Suggested-by: Paolo Abeni <pabeni@redhat.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index d5d22c41191826d68a3eefeeeb2380dfc0227586..4525d6256321f971f60183086b497abf7e3f74df 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2007,15 +2007,14 @@ struct tcp_request_sock_ops {
                                          const struct sock *sk,
                                          const struct sk_buff *skb);
 #endif
-       void (*init_req)(struct request_sock *req,
-                        const struct sock *sk_listener,
-                        struct sk_buff *skb);
 #ifdef CONFIG_SYN_COOKIES
        __u32 (*cookie_init_seq)(const struct sk_buff *skb,
                                 __u16 *mss);
 #endif
-       struct dst_entry *(*route_req)(const struct sock *sk, struct flowi *fl,
-                                      const struct request_sock *req);
+       struct dst_entry *(*route_req)(const struct sock *sk,
+                                      struct sk_buff *skb,
+                                      struct flowi *fl,
+                                      struct request_sock *req);
        u32 (*init_seq)(const struct sk_buff *skb);
        u32 (*init_ts_off)(const struct net *net, const struct sk_buff *skb);
        int (*send_synack)(const struct sock *sk, struct dst_entry *dst,

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index fb3a7750f6238356bf96cca0645529a374189cd1..9e8a6c1aa0190cc248b3b99b073a4c6e45884cf5 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6799,18 +6799,13 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
        /* Note: tcp_v6_init_req() might override ir_iif for link locals */
        inet_rsk(req)->ir_iif = inet_request_bound_dev_if(sk, skb);
 
-       af_ops->init_req(req, sk, skb);
-
-       if (security_inet_conn_request(sk, skb, req))
+       dst = af_ops->route_req(sk, skb, &fl, req);
+       if (!dst)
                goto drop_and_free;
 
        if (tmp_opt.tstamp_ok)
                tcp_rsk(req)->ts_off = af_ops->init_ts_off(net, skb);
 
-       dst = af_ops->route_req(sk, &fl, req);
-       if (!dst)
-               goto drop_and_free;
-
        if (!want_cookie && !isn) {
                /* Kill the following clause, if you dislike this way. */
                if (!net->ipv4.sysctl_tcp_syncookies &&

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index e4b31e70bd301cd07f520d07684e5e5f94b18f74..af2338294598d0823a3de4ca6bcdac1ef330d85d 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1444,9 +1444,15 @@ static void tcp_v4_init_req(struct request_sock *req,
 }
 
 static struct dst_entry *tcp_v4_route_req(const struct sock *sk,
+                                         struct sk_buff *skb,
                                          struct flowi *fl,
-                                         const struct request_sock *req)
+                                         struct request_sock *req)
 {
+       tcp_v4_init_req(req, sk, skb);
+
+       if (security_inet_conn_request(sk, skb, req))
+               return NULL;
+
        return inet_csk_route_req(sk, &fl->u.ip4, req);
 }
 
@@ -1466,7 +1472,6 @@ const struct tcp_request_sock_ops tcp_request_sock_ipv4_ops = {
        .req_md5_lookup =       tcp_v4_md5_lookup,
        .calc_md5_hash  =       tcp_v4_md5_hash_skb,
 #endif
-       .init_req       =       tcp_v4_init_req,
 #ifdef CONFIG_SYN_COOKIES
        .cookie_init_seq =      cookie_v4_init_sequence,
 #endif

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 992cbf3eb9e38b3c5318d2aa5b7dc49e08db7439..1a15105137397be158cc4a5357513b4e1b82bf97 100644 (file)
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -828,9 +828,15 @@ static void tcp_v6_init_req(struct request_sock *req,
 }
 
 static struct dst_entry *tcp_v6_route_req(const struct sock *sk,
+                                         struct sk_buff *skb,
                                          struct flowi *fl,
-                                         const struct request_sock *req)
+                                         struct request_sock *req)
 {
+       tcp_v6_init_req(req, sk, skb);
+
+       if (security_inet_conn_request(sk, skb, req))
+               return NULL;
+
        return inet6_csk_route_req(sk, &fl->u.ip6, req, IPPROTO_TCP);
 }
 
@@ -851,7 +857,6 @@ const struct tcp_request_sock_ops tcp_request_sock_ipv6_ops = {
        .req_md5_lookup =       tcp_v6_md5_lookup,
        .calc_md5_hash  =       tcp_v6_md5_hash_skb,
 #endif
-       .init_req       =       tcp_v6_init_req,
 #ifdef CONFIG_SYN_COOKIES
        .cookie_init_seq =      cookie_v6_init_sequence,
 #endif

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 023c856424b708df2016ee555d89c6afd685a79e..727e607f40d2260ccbb62fb6ea36ff00c11822f1 100644 (file)
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -228,27 +228,39 @@ int mptcp_subflow_init_cookie_req(struct request_sock *req,
 }
 EXPORT_SYMBOL_GPL(mptcp_subflow_init_cookie_req);
 
-static void subflow_v4_init_req(struct request_sock *req,
-                               const struct sock *sk_listener,
-                               struct sk_buff *skb)
+static struct dst_entry *subflow_v4_route_req(const struct sock *sk,
+                                             struct sk_buff *skb,
+                                             struct flowi *fl,
+                                             struct request_sock *req)
 {
+       struct dst_entry *dst;
+
        tcp_rsk(req)->is_mptcp = 1;
 
-       tcp_request_sock_ipv4_ops.init_req(req, sk_listener, skb);
+       dst = tcp_request_sock_ipv4_ops.route_req(sk, skb, fl, req);
+       if (!dst)
+               return NULL;
 
-       subflow_init_req(req, sk_listener, skb);
+       subflow_init_req(req, sk, skb);
+       return dst;
 }
 
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
-static void subflow_v6_init_req(struct request_sock *req,
-                               const struct sock *sk_listener,
-                               struct sk_buff *skb)
+static struct dst_entry *subflow_v6_route_req(const struct sock *sk,
+                                             struct sk_buff *skb,
+                                             struct flowi *fl,
+                                             struct request_sock *req)
 {
+       struct dst_entry *dst;
+
        tcp_rsk(req)->is_mptcp = 1;
 
-       tcp_request_sock_ipv6_ops.init_req(req, sk_listener, skb);
+       dst = tcp_request_sock_ipv6_ops.route_req(sk, skb, fl, req);
+       if (!dst)
+               return NULL;
 
-       subflow_init_req(req, sk_listener, skb);
+       subflow_init_req(req, sk, skb);
+       return dst;
 }
 #endif
 
@@ -1388,7 +1400,7 @@ void __init mptcp_subflow_init(void)
                panic("MPTCP: failed to init subflow request sock ops\n");
 
        subflow_request_sock_ipv4_ops = tcp_request_sock_ipv4_ops;
-       subflow_request_sock_ipv4_ops.init_req = subflow_v4_init_req;
+       subflow_request_sock_ipv4_ops.route_req = subflow_v4_route_req;
 
        subflow_specific = ipv4_specific;
        subflow_specific.conn_request = subflow_v4_conn_request;
@@ -1397,7 +1409,7 @@ void __init mptcp_subflow_init(void)
 
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
        subflow_request_sock_ipv6_ops = tcp_request_sock_ipv6_ops;
-       subflow_request_sock_ipv6_ops.init_req = subflow_v6_init_req;
+       subflow_request_sock_ipv6_ops.route_req = subflow_v6_route_req;
 
        subflow_v6_specific = ipv6_specific;
        subflow_v6_specific.conn_request = subflow_v6_conn_request;