[PATCH net-next 5/8] mptcp: cleanup subflow_finish_connect()

[Paolo Abeni]

The mentioned function has several unneeded branches,
handle each case - MP_CAPABLE, MP_JOIN, fallback -
under a single conditional and drop quite a bit of
duplicate code.

Reviewed-by: Mat Martineau <mathew.j.martin...@linux.intel.com>
Tested-by: Christoph Paasch <cpaa...@apple.com>
Signed-off-by: Paolo Abeni <pab...@redhat.com>
---
 net/mptcp/subflow.c | 56 ++++++++++++++++++++-------------------------
 1 file changed, 25 insertions(+), 31 deletions(-)

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index ea81842fc3b2..7f3ef1840df5 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -206,44 +206,34 @@ static void subflow_finish_connect(struct sock *sk, const 
struct sk_buff *skb)
        pr_debug("subflow=%p synack seq=%x", subflow, subflow->ssn_offset);
 
        mptcp_get_options(skb, &mp_opt);
-       if (subflow->request_mptcp && mp_opt.mp_capable) {
+       if (subflow->request_mptcp) {
+               if (!mp_opt.mp_capable) {
+                       MPTCP_INC_STATS(sock_net(sk),
+                                       MPTCP_MIB_MPCAPABLEACTIVEFALLBACK);
+                       mptcp_do_fallback(sk);
+                       pr_fallback(mptcp_sk(subflow->conn));
+                       goto fallback;
+               }
+
                subflow->mp_capable = 1;
                subflow->can_ack = 1;
                subflow->remote_key = mp_opt.sndr_key;
                pr_debug("subflow=%p, remote_key=%llu", subflow,
                         subflow->remote_key);
-       } else if (subflow->request_join && mp_opt.mp_join) {
-               subflow->mp_join = 1;
+               mptcp_finish_connect(sk);
+       } else if (subflow->request_join) {
+               u8 hmac[SHA256_DIGEST_SIZE];
+
+               if (!mp_opt.mp_join)
+                       goto do_reset;
+
                subflow->thmac = mp_opt.thmac;
                subflow->remote_nonce = mp_opt.nonce;
                pr_debug("subflow=%p, thmac=%llu, remote_nonce=%u", subflow,
                         subflow->thmac, subflow->remote_nonce);
-       } else {
-               if (subflow->request_mptcp)
-                       MPTCP_INC_STATS(sock_net(sk),
-                                       MPTCP_MIB_MPCAPABLEACTIVEFALLBACK);
-               mptcp_do_fallback(sk);
-               pr_fallback(mptcp_sk(subflow->conn));
-       }
 
-       if (mptcp_check_fallback(sk)) {
-               mptcp_rcv_space_init(mptcp_sk(parent), sk);
-               return;
-       }
-
-       if (subflow->mp_capable) {
-               pr_debug("subflow=%p, remote_key=%llu", mptcp_subflow_ctx(sk),
-                        subflow->remote_key);
-               mptcp_finish_connect(sk);
-       } else if (subflow->mp_join) {
-               u8 hmac[SHA256_DIGEST_SIZE];
-
-               pr_debug("subflow=%p, thmac=%llu, remote_nonce=%u",
-                        subflow, subflow->thmac,
-                        subflow->remote_nonce);
                if (!subflow_thmac_valid(subflow)) {
                        MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINACKMAC);
-                       subflow->mp_join = 0;
                        goto do_reset;
                }
 
@@ -251,18 +241,22 @@ static void subflow_finish_connect(struct sock *sk, const 
struct sk_buff *skb)
                                      subflow->local_nonce,
                                      subflow->remote_nonce,
                                      hmac);
-
                memcpy(subflow->hmac, hmac, MPTCPOPT_HMAC_LEN);
 
                if (!mptcp_finish_join(sk))
                        goto do_reset;
 
+               subflow->mp_join = 1;
                MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNACKRX);
-       } else {
-do_reset:
-               tcp_send_active_reset(sk, GFP_ATOMIC);
-               tcp_done(sk);
+       } else if (mptcp_check_fallback(sk)) {
+fallback:
+               mptcp_rcv_space_init(mptcp_sk(parent), sk);
        }
+       return;
+
+do_reset:
+       tcp_send_active_reset(sk, GFP_ATOMIC);
+       tcp_done(sk);
 }
 
 static struct request_sock_ops subflow_request_sock_ops;
-- 
2.26.2