mptcp: pm: avoid computing add_addr size twice

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@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260605-net-next-mptcp-add-addr6-port-ts-v2-3-758e7ca73f4d@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index e44db4768f6cf2d0ada5588b9882988c7511e2c3..2e4b6aafbad55c01a339befce41b9ac16ce17d6d 100644 (file)
--- 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 4bc380c6f0e153fc47c5b989df33e930b22bb0f6..59dc598d343dd5b5d654b76eb578419fc63b800e 100644 (file)
--- 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 75c5faaf4486e0d09f3493820b674821c7122a2b..4dfea209ac165729d7edec341b9944f0c2e44ee7 100644 (file)
--- 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);