From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 24B063F23A6 for ; Wed, 5 Aug 2026 16:43:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785948210; cv=none; b=i6aDu3vg4KAaIFjTAcv6s7pzJUVzxXrF5vsEC8cvey2yKl8x/ZUOqOFlu93Iq0Y4ZTU+ZVnANlnN6bc1ftkTjFUqm7RADqg2pJSfPDSrayaRaTAcdK9NGBW2ABBKsanc+vM7/XWQrZ6g4E743rQDlJwDASqo3rwAi6OIwUZkR/Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785948210; c=relaxed/simple; bh=svXov/+/qacZXuCaADwR0fARBj86nQMY51zilcm/8c0=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=e1tz5aZtLr0ClkliU05Qi5HQIJoziGVuCpLMGlQ9Cc9/3zi1Ivdr/JfHdTSupLvcEanTYaw1IezGGx7FU0RQYAnr5fksWPW5sbn174aWBJBGzZXkpsrH+lUjGkldkJQeIWSqjFeXhAaFw92n+JsD32ggRN0ZtIKJnRCHD4I4X+Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=M0a1a1Dw; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="M0a1a1Dw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B36221F000E9 for ; Wed, 5 Aug 2026 16:43:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785948209; bh=tji+GcZCXBNfxnDnTeLhiBD3OHZ6C0En0VGACUwku6Q=; h=Date:Subject:To:References:From:In-Reply-To; b=M0a1a1DwhniKJ8E3n81dueh2w8TNyAe26tgs92Aztghuk5NdTUe1u2qYJAcM/Pcoj +olMxcqFNy54uaQUzj374e3yADKMO29W+zpcfHCSvlNntiQVkJycqTcKl22EQ/UN1a nC1/8bAGC0EzUL9OopSsFXCViNZAK/VsmhfK0o+5joBnQ5jIVgRJOObx+DPCZLRNub ZQkXWvDErTUDqvAfWhemOFfFX6e48w3LjH/usmV/nce4+QPSyfDj5eLXP3HbwZgoC9 jxnOomyd/ie8lZxN3Ge6WojeqoYATPuutr/rOtz0d4jHmZyKUYQBUvvPbMJU1SVHFd UaGhMprNHPzEA== Message-ID: <68abb788-0804-4afe-8c0d-b4b6d566c365@kernel.org> Date: Wed, 5 Aug 2026 18:43:27 +0200 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH mptcp-net 1/6] mptcp: pm: userspace: properly handle the ID0 case Content-Language: fr To: MPTCP Linux References: <20260727-mptcp-pm-userspace-id0-case-v1-0-9877f02a9bae@kernel.org> <20260727-mptcp-pm-userspace-id0-case-v1-1-9877f02a9bae@kernel.org> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Replying to Sashiko's review: >> diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c >> index 73094bdbdbf27..6e6eeda91ade0 100644 >> --- a/net/mptcp/pm_userspace.c >> +++ b/net/mptcp/pm_userspace.c >> @@ -55,7 +55,10 @@ static int mptcp_userspace_pm_append_new_local_addr(struct mptcp_sock *msk, >> >> spin_lock_bh(&msk->pm.lock); >> mptcp_for_each_userspace_pm_addr(msk, e) { >> - addr_match = mptcp_addresses_equal(&e->addr, &entry->addr, true); >> + /* allow matching ID0 when no port is specified */ >> + addr_match = mptcp_addresses_equal(&e->addr, &entry->addr, >> + e->addr.id != 0 || >> + entry->addr.port != 0); >> if (addr_match && entry->addr.id == 0 && needs_id) >> entry->addr.id = e->addr.id; >> id_match = (e->addr.id == entry->addr.id); >> if (addr_match || id_match) >> break; > > With ID 0 now always present in userspace_pm_local_addr_list, does this > id_match check prematurely break the loop for new unassigned addresses? > > If an unconfigured address is evaluated (e.g. from an incoming MP_JOIN > request), entry->addr.id defaults to 0. Since the pre-added initial address > (ID 0) is now in the list, e->addr.id == entry->addr.id (0 == 0) will be > true, falsely detecting an ID collision and preventing the new address from > being inserted. I guess it meant "if the IP address is not the same". If it is, now the right ID0 will be returned instead of a new one. If the address is different, then yes, id_match should always be false when needs_id is set. I will adapt that in a v2. (The bug was also present before when the ID0 was in the list.) >> @@ -692,6 +695,24 @@ int mptcp_userspace_pm_get_addr(u8 id, struct mptcp_pm_addr_entry *addr, >> return ret; >> } >> >> +/* Add the initial local address (ID0) to the local list: easier that way */ >> +void mptcp_pm_userspace_created(struct mptcp_sock *msk, const struct sock *ssk) >> +{ >> + struct mptcp_pm_addr_entry *entry; >> + >> + entry = sock_kmalloc((struct sock *)msk, sizeof(*entry), GFP_ATOMIC); >> + /* Fine not to handle the ID0 case in memory pressure */ >> + if (!entry) >> + return; >> + >> + memset(entry, 0, sizeof(*entry)); >> + mptcp_local_address((struct sock_common *)ssk, &entry->addr); >> + >> + spin_lock_bh(&msk->pm.lock); >> + list_add_tail_rcu(&entry->list, &msk->pm.userspace_pm_local_addr_list); > > Does this code forget to increment msk->pm.local_addr_used? No, on purpose. > When this address is added here, the counter is not incremented. Later, if > userspace creates a subflow using ID 0 and destroys it, or if subflow creation > fails, mptcp_userspace_pm_delete_local_addr() will unconditionally decrement > msk->pm.local_addr_used. This could cause the counter to underflow to 255 > and permanently remove the ID 0 address from the list. Indeed, an exception is needed there. Will add that in v2. > >> + spin_unlock_bh(&msk->pm.lock); >> +} Cheers, Matt -- Sponsored by the NGI0 Core fund.