mptcp: pm: avoid computing rm_addr size twice

mptcp_rm_addr_len helper was called twice: in mptcp_pm_rm_addr_signal,
then just after in mptcp_established_options_rm_addr. Both to check the
remaining space.

The second call is not needed: if there is not enough space,
mptcp_pm_rm_addr_signal will return false, and the caller,
mptcp_established_options_rm_addr, will do the same without re-checking
the size again. Instead, mptcp_pm_rm_addr_signal can directly set the
size.

While at it, move mptcp_rm_addr_len to pm.c, as it is now only used
there, once.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260605-net-next-mptcp-add-addr6-port-ts-v2-2-758e7ca73f4d@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/options.c

@@ -711,19 +711,12 @@ static bool mptcp_established_options_rm_addr(struct sock *sk, int *size,
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 	struct mptcp_rm_list rm_list;
-	int i, len;
+	int i;
 
 	if (!mptcp_pm_should_rm_signal(msk) ||
-	    !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_list)))
+	    !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_list, size)))
 		return false;
 
-	len = mptcp_rm_addr_len(&rm_list);
-	if (len < 0)
-		return false;
-	if (remaining < len)
-		return false;
-
-	*size = len;
 	opts->suboptions |= OPTION_MPTCP_RM_ADDR;
 	opts->rm_list = rm_list;
 

net/mptcp/pm.c

@@ -953,8 +953,16 @@ out_unlock:
 	return ret;
 }
 
+static int mptcp_rm_addr_len(const struct mptcp_rm_list *rm_list)
+{
+	if (rm_list->nr == 0 || rm_list->nr > MPTCP_RM_IDS_MAX)
+		return -EINVAL;
+
+	return TCPOLEN_MPTCP_RM_ADDR_BASE + roundup(rm_list->nr - 1, 4) + 1;
+}
+
 bool mptcp_pm_rm_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
-			     struct mptcp_rm_list *rm_list)
+			     struct mptcp_rm_list *rm_list, int *size)
 {
 	int ret = false, len;
 	u8 rm_addr;
@@ -974,6 +982,7 @@ bool mptcp_pm_rm_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
 	if (remaining < len)
 		goto out_unlock;
 
+	*size = len;
 	*rm_list = msk->pm.rm_list_tx;
 	WRITE_ONCE(msk->pm.addr_signal, rm_addr);
 	ret = true;

net/mptcp/protocol.h

@@ -1221,19 +1221,11 @@ static inline unsigned int mptcp_add_addr_len(int family, bool echo, bool port)
 	return len;
 }
 
-static inline int mptcp_rm_addr_len(const struct mptcp_rm_list *rm_list)
-{
-	if (rm_list->nr == 0 || rm_list->nr > MPTCP_RM_IDS_MAX)
-		return -EINVAL;
-
-	return TCPOLEN_MPTCP_RM_ADDR_BASE + roundup(rm_list->nr - 1, 4) + 1;
-}
-
 bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int opt_size,
 			      unsigned int remaining,
 			      struct mptcp_addr_info *addr, bool *echo);
 bool mptcp_pm_rm_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
-			     struct mptcp_rm_list *rm_list);
+			     struct mptcp_rm_list *rm_list, int *len);
 int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc);
 int mptcp_pm_nl_get_local_id(struct mptcp_sock *msk,
 			     struct mptcp_pm_addr_entry *skc);