From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: passt.top; dmarc=none (p=none dis=none) header.from=gibson.dropbear.id.au Authentication-Results: passt.top; dkim=pass (2048-bit key; secure) header.d=gibson.dropbear.id.au header.i=@gibson.dropbear.id.au header.a=rsa-sha256 header.s=202512 header.b=PBikRuOu; dkim-atps=neutral Received: from mail.ozlabs.org (mail.ozlabs.org [IPv6:2404:9400:2221:ea00::3]) by passt.top (Postfix) with ESMTPS id AC3035A0625 for ; Thu, 08 Jan 2026 03:29:52 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gibson.dropbear.id.au; s=202512; t=1767839390; bh=yB6q+1rvW2lyneVCEPmOyJoDBCuWMb59HJbrnPB7GrM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PBikRuOuysKlxWzzOkIZDU/IbdDg5zi0dLUA9JWx96UvkOSaSlobPW+VDxHcxo4C6 P4cNJ3OUvIpoL5DnU0Nu1xaRhT+nxnomZ4xQLPhZrRSUzLHN5ojeBCqs34nRDv8sr2 6I42WLJyx4+6vAvTAr0/CgRW0AEeNmjQaypn9HC8zwMVhSY92h7tg8Nusb/Eu8NnuH m/VMq54+e0pseXZoNzkTFrx49EToWLMZbT+v/Pjt33glIKnwci/m6E/soEx11udJ58 TuE36WUT4HpEAwlzVdqzcm06MrDgyZPa4KVioYxKsjmsWRGEDK64TtxlNYEg12xhN4 KUP+YVEW1fBjQ== Received: by gandalf.ozlabs.org (Postfix, from userid 1007) id 4dmplL3M6cz4wR9; Thu, 08 Jan 2026 13:29:50 +1100 (AEDT) From: David Gibson To: Stefano Brivio , passt-dev@passt.top Subject: [PATCH v3 03/14] conf: Accurately record ifname and address for outbound forwards Date: Thu, 8 Jan 2026 13:29:37 +1100 Message-ID: <20260108022948.2657573-4-david@gibson.dropbear.id.au> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260108022948.2657573-1-david@gibson.dropbear.id.au> References: <20260108022948.2657573-1-david@gibson.dropbear.id.au> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-ID-Hash: DMUGNK2B4UGGIPSX63RQJPU3SO6GLWYE X-Message-ID-Hash: DMUGNK2B4UGGIPSX63RQJPU3SO6GLWYE X-MailFrom: dgibson@gandalf.ozlabs.org X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: David Gibson X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: -T and -U options don't allow specifying a listening address. Usually this will listen on *%lo in the guest. However on kernels without unprivileged SO_BINDTODEVICE that's not possible so we instead listen separately on 127.0.0.1 and ::1. Currently that's handled at the point we actually set up the listens, we record both address and ifname as NULL in the forwarding table entry. That will cause trouble for future extensions we want, so update this to accurately create the forwarding table: either a single rule with ifname == "lo" or two rules with addresses of 127.0.0.1 and ::1. As a bonus, this gives the user a warning if they specify an explicit outbound forwarding on a kernel without SO_BINDTODEVICE. The existing warning for missing SO_BINDTODEVICE incorrectly covered only the case of -T auto or -U auto. Signed-off-by: David Gibson --- conf.c | 38 ++++++++++++++++++++++++++++++-------- 1 file changed, 30 insertions(+), 8 deletions(-) diff --git a/conf.c b/conf.c index 127e69f5..b486fefe 100644 --- a/conf.c +++ b/conf.c @@ -157,12 +157,6 @@ static void conf_ports_range_except(const struct ctx *c, char optname, optname, optarg); } - if (ifname && c->no_bindtodevice) { - die( -"Device binding for '-%c %s' unsupported (requires kernel 5.7+)", - optname, optarg); - } - if (addr) { if (!c->ifi4 && inany_v4(addr)) { die("IPv4 is disabled, can't use -%c %s", @@ -209,8 +203,27 @@ static void conf_ports_range_except(const struct ctx *c, char optname, } } - fwd_rule_add(fwd, flags, addr, ifname, base, i - 1, - base + delta); + if ((optname == 'T' || optname == 'U') && c->no_bindtodevice) { + /* FIXME: Once the fwd bitmaps are removed, move this + * workaround to the caller + */ + ASSERT(!addr && ifname && !strcmp(ifname, "lo")); + warn( +"SO_BINDTODEVICE unavailable, forwarding only 127.0.0.1 and ::1 for '-%c %s'", + optname, optarg); + + if (c->ifi4) { + fwd_rule_add(fwd, flags, &inany_loopback4, NULL, + base, i - 1, base + delta); + } + if (c->ifi6) { + fwd_rule_add(fwd, flags, &inany_loopback6, NULL, + base, i - 1, base + delta); + } + } else { + fwd_rule_add(fwd, flags, addr, ifname, + base, i - 1, base + delta); + } base = i - 1; } @@ -357,6 +370,15 @@ static void conf_ports(const struct ctx *c, char optname, const char *optarg, } } while ((p = next_chunk(p, ','))); + if (ifname && c->no_bindtodevice) { + die( +"Device binding for '-%c %s' unsupported (requires kernel 5.7+)", + optname, optarg); + } + /* Outbound forwards come from guest loopback */ + if ((optname == 'T' || optname == 'U') && !ifname) + ifname = "lo"; + if (exclude_only) { /* Exclude ephemeral ports */ for (i = 0; i < NUM_PORTS; i++) -- 2.52.0