Since its introduction in commit 892f396c8e68 ("mptcp: netlink: issue
MP_PRIO signals from userspace PMs"), it was mandatory to specify the
remote address, because of the 'if (rem->addr.family == AF_UNSPEC)'
check done later one.

In theory, this attribute can be optional, but it sounds better to be
precise to avoid sending the MP_PRIO on the wrong subflow, e.g. if there
are multiple subflows attached to the same local ID. This can be relaxed
later on if there is a need to act on multiple subflows with one
command.

For the moment, the check to see if attr_rem is NULL can be removed,
because mptcp_pm_parse_entry() will do this check as well, no need to do
that differently here.

Reviewed-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/pm_userspace.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
index 4de38bc03ab8add367720262f353dd20cacac108..b6cf8ea1161ddc7f0f1662320aebfe720f55e722 100644
--- a/net/mptcp/pm_userspace.c
+++ b/net/mptcp/pm_userspace.c
@@ -580,11 +580,9 @@ int mptcp_userspace_pm_set_flags(struct sk_buff *skb, struct genl_info *info)
 	if (ret < 0)
 		goto set_flags_err;
 
-	if (attr_rem) {
-		ret = mptcp_pm_parse_entry(attr_rem, info, false, &rem);
-		if (ret < 0)
-			goto set_flags_err;
-	}
+	ret = mptcp_pm_parse_entry(attr_rem, info, false, &rem);
+	if (ret < 0)
+		goto set_flags_err;
 
 	if (loc.addr.family == AF_UNSPEC ||
 	    rem.addr.family == AF_UNSPEC) {

-- 
2.47.1

On Fri, Feb 07, 2025 at 02:59:20PM +0100, Matthieu Baerts (NGI0) wrote:
> Since its introduction in commit 892f396c8e68 ("mptcp: netlink: issue
> MP_PRIO signals from userspace PMs"), it was mandatory to specify the
> remote address, because of the 'if (rem->addr.family == AF_UNSPEC)'
> check done later one.
> 
> In theory, this attribute can be optional, but it sounds better to be
> precise to avoid sending the MP_PRIO on the wrong subflow, e.g. if there
> are multiple subflows attached to the same local ID. This can be relaxed
> later on if there is a need to act on multiple subflows with one
> command.
> 
> For the moment, the check to see if attr_rem is NULL can be removed,
> because mptcp_pm_parse_entry() will do this check as well, no need to do
> that differently here.
> 
> Reviewed-by: Geliang Tang <geliang@kernel.org>
> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>

Reviewed-by: Simon Horman <horms@kernel.org>