Merge branch 'mptcp-fix-MP_JOIN-failure-handling'

Paolo Abeni says:

====================
mptcp: fix MP_JOIN failure handling

Currently if we hit an MP_JOIN failure on the third ack, the child socket is
closed with reset, but the request socket is not deleted, causing weird
behaviors.

The main problem is that MPTCP's MP_JOIN code needs to plug it's own
'valid 3rd ack' checks and the current TCP callbacks do not allow that.

This series tries to address the above shortcoming introducing a new MPTCP
specific bit in a 'struct tcp_request_sock' hole, and leveraging that to allow
tcp_check_req releasing the request socket when needed.

The above allows cleaning-up a bit current MPTCP hooking in tcp_check_req().

An alternative solution, possibly cleaner but more invasive, would be
changing the 'bool *own_req' syn_recv_sock() argument into 'int *req_status'
and let MPTCP set it to 'REQ_DROP'.

v1 -> v2:
 - be more conservative about drop_req initialization

RFC -> v1:
 - move the drop_req bit inside tcp_request_sock (Eric)
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 7 deletions

diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index e60275659de6..c4a6ef4ba35b 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -68,6 +68,11 @@ static inline bool rsk_is_mptcp(const struct request_sock *req)
 	return tcp_rsk(req)->is_mptcp;
 }
 
+static inline bool rsk_drop_req(const struct request_sock *req)
+{
+	return tcp_rsk(req)->is_mptcp && tcp_rsk(req)->drop_req;
+}
+
 void mptcp_space(const struct sock *ssk, int *space, int *full_space);
 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 		       unsigned int *size, struct mptcp_out_options *opts);
@@ -121,8 +126,6 @@ static inline bool mptcp_skb_can_collapse(const struct sk_buff *to,
 				 skb_ext_find(from, SKB_EXT_MPTCP));
 }
 
-bool mptcp_sk_is_subflow(const struct sock *sk);
-
 void mptcp_seq_show(struct seq_file *seq);
 #else
 
@@ -140,6 +143,11 @@ static inline bool rsk_is_mptcp(const struct request_sock *req)
 	return false;
 }
 
+static inline bool rsk_drop_req(const struct request_sock *req)
+{
+	return false;
+}
+
 static inline void mptcp_parse_option(const struct sk_buff *skb,
 				      const unsigned char *ptr, int opsize,
 				      struct tcp_options_received *opt_rx)
@@ -190,11 +198,6 @@ static inline bool mptcp_skb_can_collapse(const struct sk_buff *to,
 	return true;
 }
 
-static inline bool mptcp_sk_is_subflow(const struct sock *sk)
-{
-	return false;
-}
-
 static inline void mptcp_space(const struct sock *ssk, int *s, int *fs) { }
 static inline void mptcp_seq_show(struct seq_file *seq) { }
 #endif /* CONFIG_MPTCP */