[PATCH net-next v2 03/15] mptcp: pm: avoid computing add_addr size twice

[Matthieu Baerts (NGI0)]

mptcp_add_addr_len helper was called twice: in mptcp_pm_add_addr_signal,
then just after in mptcp_established_options_add_addr. Both to check
the remaining space.

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

Note that the returned size can be negative when other suboptions are
dropped, e.g. to send an echo ADD_ADDR with a v4 address, and no port.

While at it:

 - move mptcp_add_addr_len to pm.c, as it is now only used from there

 - use 'int' in mptcp_add_addr_len for the size, instead of having a mix

 - use a bool for 'ret' in mptcp_pm_add_addr_signal

Reviewed-by: Mat Martineau <martineau@xxxxxxxxxx>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx>
---
 net/mptcp/options.c  | 15 ++-------------
 net/mptcp/pm.c       | 27 ++++++++++++++++++++++-----
 net/mptcp/protocol.h | 18 +-----------------
 3 files changed, 25 insertions(+), 35 deletions(-)

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index e44db4768f6c..2e4b6aafbad5 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -663,10 +663,8 @@ static bool mptcp_established_options_add_addr(struct sock *sk,
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
-	unsigned int opt_size = *size;
 	struct mptcp_addr_info addr;
 	bool echo;
-	int len;
 
 	/* add addr will strip the existing options, be sure to avoid breaking
 	 * MPC/MPJ handshakes
@@ -674,21 +672,12 @@ static bool mptcp_established_options_add_addr(struct sock *sk,
 	if (!mptcp_pm_should_add_signal(msk) ||
 	    (opts->suboptions & (OPTION_MPTCP_MPJ_ACK | OPTION_MPTCP_MPC_ACK)) ||
 	    !skb || !skb_is_tcp_pure_ack(skb) ||
-	    !mptcp_pm_add_addr_signal(msk, opt_size, remaining, &addr, &echo))
+	    !mptcp_pm_add_addr_signal(msk, size, remaining, &addr, &echo))
 		return false;
 
-	remaining += opt_size;
-
-	len = mptcp_add_addr_len(addr.family, echo, !!addr.port);
-	if (remaining < len)
-		return false;
-
-	*size = len;
 	pr_debug("drop other suboptions\n");
-	opts->suboptions = 0;
-	*size -= opt_size;
+	opts->suboptions = OPTION_MPTCP_ADD_ADDR;
 	opts->addr = addr;
-	opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 	if (!echo) {
 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDRTX);
 		opts->ahmac = add_addr_generate_hmac(READ_ONCE(msk->local_key),
diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
index 4bc380c6f0e1..59dc598d343d 100644
--- a/net/mptcp/pm.c
+++ b/net/mptcp/pm.c
@@ -887,13 +887,28 @@ void mptcp_pm_mp_fail_received(struct sock *sk, u64 fail_seq)
 	}
 }
 
-bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int opt_size,
-			      unsigned int remaining,
+static int mptcp_add_addr_len(int family, bool echo, bool port)
+{
+	int len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
+
+	if (family == AF_INET6)
+		len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
+	if (!echo)
+		len += MPTCPOPT_THMAC_LEN;
+	/* account for 2 trailing 'nop' options */
+	if (port)
+		len += TCPOLEN_MPTCP_PORT_LEN + TCPOLEN_MPTCP_PORT_ALIGN;
+
+	return len;
+}
+
+bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, int *size, int remaining,
 			      struct mptcp_addr_info *addr, bool *echo)
 {
 	bool skip_add_addr = false;
-	int ret = false;
+	bool ret = false;
 	u8 add_addr;
+	int len = 0;
 	u8 family;
 	bool port;
 
@@ -907,7 +922,7 @@ bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int opt_size,
 	 * plain dup-ack from TCP perspective. The other MPTCP-relevant info,
 	 * if any, will be carried by the 'original' TCP ack
 	 */
-	remaining += opt_size;
+	len -= *size;
 
 	*echo = mptcp_pm_should_add_signal_echo(msk);
 	if (*echo) {
@@ -922,7 +937,8 @@ bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int opt_size,
 		family = msk->pm.local.family;
 	}
 
-	if (remaining < mptcp_add_addr_len(family, *echo, port)) {
+	len += mptcp_add_addr_len(family, *echo, port);
+	if (len > remaining) {
 		struct net *net = sock_net((struct sock *)msk);
 
 		if (*echo) {
@@ -935,6 +951,7 @@ bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int opt_size,
 	}
 
 	ret = true;
+	*size = len;
 
 drop_signal_mark:
 	WRITE_ONCE(msk->pm.addr_signal, add_addr);
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 75c5faaf4486..4dfea209ac16 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -1206,23 +1206,7 @@ static inline bool mptcp_pm_is_kernel(const struct mptcp_sock *msk)
 	return READ_ONCE(msk->pm.pm_type) == MPTCP_PM_TYPE_KERNEL;
 }
 
-static inline unsigned int mptcp_add_addr_len(int family, bool echo, bool port)
-{
-	u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
-
-	if (family == AF_INET6)
-		len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
-	if (!echo)
-		len += MPTCPOPT_THMAC_LEN;
-	/* account for 2 trailing 'nop' options */
-	if (port)
-		len += TCPOLEN_MPTCP_PORT_LEN + TCPOLEN_MPTCP_PORT_ALIGN;
-
-	return len;
-}
-
-bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int opt_size,
-			      unsigned int remaining,
+bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, int *size, 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, int *len);

-- 
2.53.0