Re: [PATCH mptcp-net v3 2/8] mptcp: pm: userspace: lookup: match port in priority

Hi Matt,

On Fri, 2026-08-07 at 10:41 +0200, Matthieu Baerts (NGI0) wrote:
> In the local address list, there can be entries with the port set to
> 0
> -- corresponding to the source port used by the initial subflow --
> and
> others with a specific port.
> 
> When performing a lookup, it is important to compare the ports to
> pick
> the right entry: when a specific port is given, then try to match it
> first. If no match is found, try to find entries with the port set to
> 0.
> 
> Fixes: 24430f8bf516 ("mptcp: add address into userspace pm list")
> Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>
> ---
> v3: new (Sashiko)
> ---
>  net/mptcp/pm_userspace.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
> index 663cbeb79548..3f1471ec3fc7 100644
> --- a/net/mptcp/pm_userspace.c
> +++ b/net/mptcp/pm_userspace.c
> @@ -33,10 +33,22 @@ mptcp_userspace_pm_lookup_addr(struct mptcp_sock
> *msk,
>  {
>  	struct mptcp_pm_addr_entry *entry;
>  
> +	/* Compare ports when set in addr */
>  	mptcp_for_each_userspace_pm_addr(msk, entry) {
> -		if (mptcp_addresses_equal(&entry->addr, addr,
> false))
> +		if (mptcp_addresses_equal(&entry->addr, addr, addr-
> >port != 0))
>  			return entry;
>  	}
> +
> +	if (addr->port == 0)
> +		return NULL;
> +
> +	/* Check only wildcard ports if no exact match with the port
> */
> +	mptcp_for_each_userspace_pm_addr(msk, entry) {
> +		if (entry->addr.port == 0 &&
> +		    mptcp_addresses_equal(&entry->addr, addr,
> false))
> +			return entry;
> +	}
> +
>  	return NULL;
>  }

Personally, I think a single-pass lookup is better than a two-pass one.
I've implemented a version and it passed the tests:

static struct mptcp_pm_addr_entry *
mptcp_userspace_pm_lookup_addr(struct mptcp_sock *msk,
                               const struct mptcp_addr_info *addr)
{
    struct mptcp_pm_addr_entry *entry, *wildcard = NULL;
    struct mptcp_addr_info match;

    mptcp_for_each_userspace_pm_addr(msk, entry) {
        match = entry->addr;
        if (match.port == 0 && addr->port != 0)
            match.port = addr->port;

        if (mptcp_addresses_equal(&match, addr, addr->port != 0)) {
            if (addr->port == 0 || entry->addr.port != 0)
                return entry;

            if (!wildcard)
                wildcard = entry;
        }
    }

    return wildcard;
}

What do you think of this approach?

Also, this series has conflicts with the current export branch and
needs a rebase.

Thanks,
-Geliang