From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: passt.top; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: passt.top; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=E5e9mVoM; dkim-atps=neutral Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by passt.top (Postfix) with ESMTPS id 6E8985A0271 for ; Wed, 20 Aug 2025 05:10:15 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1755659414; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=WhyZzKnFgTkO6rrjP5sdaW7qfWQAAWeMmeRw4j2ejIw=; b=E5e9mVoM+894HH9HkrP/fpNEtfFiatUIx0pXgv5sdq/oFai72Wje0+HhNb8jOgOIkIH29C Nm82FDGT6bQitpc5awsuDEvMotjlzXZl0nXjtjLw1xD0j3cdj8eCYahRkDyYCn6mneKFAX cJQbnIBA1q9k2XbXNMtQrvqpmUYjLbw= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-495-DraZagi3NzWFQJd9ALdvwA-1; Tue, 19 Aug 2025 23:10:12 -0400 X-MC-Unique: DraZagi3NzWFQJd9ALdvwA-1 X-Mimecast-MFC-AGG-ID: DraZagi3NzWFQJd9ALdvwA_1755659412 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 20BC11956086; Wed, 20 Aug 2025 03:10:11 +0000 (UTC) Received: from jmaloy-thinkpadp16vgen1.rmtcaqc.csb (unknown [10.22.88.50]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 0DA5619A4C99; Wed, 20 Aug 2025 03:10:09 +0000 (UTC) From: Jon Maloy To: sbrivio@redhat.com, dgibson@redhat.com, david@gibson.dropbear.id.au, jmaloy@redhat.com, passt-dev@passt.top Subject: [PATCH v4 2/9] arp/ndp: respond with true MAC address of LAN local remote hosts Date: Tue, 19 Aug 2025 23:09:58 -0400 Message-ID: <20250820031005.2725591-3-jmaloy@redhat.com> In-Reply-To: <20250820031005.2725591-1-jmaloy@redhat.com> References: <20250820031005.2725591-1-jmaloy@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: IPxFO_JQpXuDdOeFFd9fPgcTNb6ue-1A53TucW5Vx7s_1755659412 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true Message-ID-Hash: EQPWJ3K7SE3H7PPU6VDPITNVO6LMZAXZ X-Message-ID-Hash: EQPWJ3K7SE3H7PPU6VDPITNVO6LMZAXZ X-MailFrom: jmaloy@redhat.com 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 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: When we receive an ARP request or NDP neigbor solicitation over the tap interface for a host on the local network segment attached to the template interface, we respond with that host's real MAC address. The local host, which is acting as a proxy for the default gateway, is still exempted from this rule. Signed-off-by: Jon Maloy --- arp.c | 9 +++++++++ fwd.c | 38 ++++++++++++++++++++++++++++++-------- fwd.h | 1 + inany.c | 1 + ndp.c | 9 +++++++++ 5 files changed, 50 insertions(+), 8 deletions(-) diff --git a/arp.c b/arp.c index fc482bb..c37867a 100644 --- a/arp.c +++ b/arp.c @@ -29,6 +29,7 @@ #include "dhcp.h" #include "passt.h" #include "tap.h" +#include "netlink.h" /** * arp() - Check if this is a supported ARP message, reply as needed @@ -39,6 +40,7 @@ */ int arp(const struct ctx *c, const struct pool *p) { + union inany_addr tgt; unsigned char swap[4]; struct ethhdr *eh; struct arphdr *ah; @@ -72,6 +74,13 @@ int arp(const struct ctx *c, const struct pool *p) memcpy(am->tha, am->sha, sizeof(am->tha)); memcpy(am->sha, c->our_tap_mac, sizeof(am->sha)); + /* Respond with true MAC address if remote host is on + * the template interface's network segment + */ + inany_from_af(&tgt, AF_INET, am->tip); + if (!fwd_inany_nat(c, &tgt)) + nl_neigh_mac_get(nl_sock, &tgt, c->ifi4, am->sha); + memcpy(swap, am->tip, sizeof(am->tip)); memcpy(am->tip, am->sip, sizeof(am->tip)); memcpy(am->sip, swap, sizeof(am->sip)); diff --git a/fwd.c b/fwd.c index 250cf56..55bf5f2 100644 --- a/fwd.c +++ b/fwd.c @@ -331,20 +331,29 @@ static bool fwd_guest_accessible(const struct ctx *c, * * Only handles translations that depend *only* on the address. Anything * related to specific ports or flows is handled elsewhere. + * + * Return: true if there was a translation, otherwise false */ -static void nat_outbound(const struct ctx *c, const union inany_addr *addr, - union inany_addr *translated) +static bool nat_outbound(const struct ctx *c, const union inany_addr *addr, + union inany_addr *translated) { - if (inany_equals4(addr, &c->ip4.map_host_loopback)) + if (inany_equals4(addr, &c->ip4.map_host_loopback)) { *translated = inany_loopback4; - else if (inany_equals6(addr, &c->ip6.map_host_loopback)) + return true; + } else if (inany_equals6(addr, &c->ip6.map_host_loopback)) { *translated = inany_loopback6; - else if (inany_equals4(addr, &c->ip4.map_guest_addr)) + return true; + } else if (inany_equals4(addr, &c->ip4.map_guest_addr)) { *translated = inany_from_v4(c->ip4.addr); - else if (inany_equals6(addr, &c->ip6.map_guest_addr)) + return true; + } else if (inany_equals6(addr, &c->ip6.map_guest_addr)) { translated->a6 = c->ip6.addr; - else - *translated = *addr; + return true; + } + + *translated = *addr; + return false; + } /** @@ -554,3 +563,16 @@ uint8_t fwd_nat_from_host(const struct ctx *c, uint8_t proto, return PIF_TAP; } + +/** fwd_inany_nat - Find if a remote IPv[46] address is subject to NAT + * @c: Execution context + * @addr: IPv[46] address + * + * Return: true if translated, false otherwise + */ +bool fwd_inany_nat(const struct ctx *c, const union inany_addr *addr) +{ + union inany_addr addr_nat; + + return nat_outbound(c, addr, &addr_nat); +} diff --git a/fwd.h b/fwd.h index 65c7c96..c8d485d 100644 --- a/fwd.h +++ b/fwd.h @@ -56,5 +56,6 @@ uint8_t fwd_nat_from_splice(const struct ctx *c, uint8_t proto, const struct flowside *ini, struct flowside *tgt); uint8_t fwd_nat_from_host(const struct ctx *c, uint8_t proto, const struct flowside *ini, struct flowside *tgt); +bool fwd_inany_nat(const struct ctx *c, const union inany_addr *addr); #endif /* FWD_H */ diff --git a/inany.c b/inany.c index 65a39f9..7680439 100644 --- a/inany.c +++ b/inany.c @@ -16,6 +16,7 @@ #include "ip.h" #include "siphash.h" #include "inany.h" +#include "fwd.h" const union inany_addr inany_loopback4 = INANY_INIT4(IN4ADDR_LOOPBACK_INIT); const union inany_addr inany_any4 = INANY_INIT4(IN4ADDR_ANY_INIT); diff --git a/ndp.c b/ndp.c index 3e15494..9912f80 100644 --- a/ndp.c +++ b/ndp.c @@ -32,6 +32,7 @@ #include "passt.h" #include "tap.h" #include "log.h" +#include "netlink.h" #define RT_LIFETIME 65535 @@ -196,6 +197,7 @@ static void ndp_send(const struct ctx *c, const struct in6_addr *dst, static void ndp_na(const struct ctx *c, const struct in6_addr *dst, const struct in6_addr *addr) { + union inany_addr tgt; struct ndp_na na = { .ih = { .icmp6_type = NA, @@ -215,6 +217,13 @@ static void ndp_na(const struct ctx *c, const struct in6_addr *dst, memcpy(na.target_l2_addr.mac, c->our_tap_mac, ETH_ALEN); + /* Respond with true link-layer address if remote host is on + * the template interface's network segment + */ + inany_from_af(&tgt, AF_INET6, addr); + if (!fwd_inany_nat(c, &tgt)) + nl_neigh_mac_get(nl_sock, &tgt, c->ifi6, na.target_l2_addr.mac); + ndp_send(c, dst, &na, sizeof(na)); } -- 2.50.1