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=fAoy3HkZ; 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 3090A5A027E for ; Wed, 10 Sep 2025 17:04:06 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1757516645; 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=BjZBX06DT787ria8Ttl7rM2Qh5wA3m9ierTV+bC73fg=; b=fAoy3HkZPvx6mTOGBX1LBQVj9ISIKnjDlwJaRewKMmHt5NdSa3aKt0BcJm5jczDeHsIz1K ayRtCILuPihLp1vS25P6E1tJsjTVDG8Pi7iN4GbjLRLEXFimr6y1QAsIZVSqCwLs26k76H fIsIMeuBo1tOiulYBs+uDYrw86ymE+Q= 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-517-YeUSWZySMwOVRJn0R2gUXA-1; Wed, 10 Sep 2025 11:04:04 -0400 X-MC-Unique: YeUSWZySMwOVRJn0R2gUXA-1 X-Mimecast-MFC-AGG-ID: YeUSWZySMwOVRJn0R2gUXA_1757516643 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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 2969C19560A0; Wed, 10 Sep 2025 15:04:03 +0000 (UTC) Received: from jmaloy-thinkpadp16vgen1.rmtcaqc.csb (unknown [10.22.88.21]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 9336A1800452; Wed, 10 Sep 2025 15:04:01 +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 v7 3/8] arp/ndp: respond with true MAC address of LAN local remote hosts Date: Wed, 10 Sep 2025 11:03:50 -0400 Message-ID: <20250910150355.366780-4-jmaloy@redhat.com> In-Reply-To: <20250910150355.366780-1-jmaloy@redhat.com> References: <20250910150355.366780-1-jmaloy@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: i5zArsZWV4twfXN8GgR_1lQ9t_FafnR2YWYdNOBcSUg_1757516643 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true Message-ID-Hash: CDXR7CA7US2MA25KNWRTJ3XEM2U6EUAR X-Message-ID-Hash: CDXR7CA7US2MA25KNWRTJ3XEM2U6EUAR 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. Signed-off-by: Jon Maloy Reviewed-by: David Gibson --- v3: - Added helper function to find out if a remote ip address is subject to NAT. This filters out local host addresses which should be presented with the passt/pasta local MAC address 9a:55:9a:55:9a:55 even though it is on the local segment. - Adapted to the change in nl_mac_get() function, so that we now consider only the template interface when checking the ARP/NDP table. v4: - Moved NAT check into the function nat_outbound() to obtain more precise criteria for when NAT is used. We may in theory have NAT even if original and translated addresses are equal, and we want to catch this case. - I chose to keep the wrapper funtion inany_nat(), but moved it to fwd.h/fwd.c and renamed it to fwd_inany_nat(). v5: - Simplified criteria for when we do ARP/NDP lookup. Now, we just try with the potentially translated address after an attempted NAT check. - Using the new ARP/NDP cache table instead of using netlink directly. v6: - Fixes after feedback from David: - Renamed nat_outbound() to fwd_nat_outbound() - Eliminated unnecessary temporary variable in arp.c::arp() --- arp.c | 9 +++++++-- fwd.c | 8 ++++---- fwd.h | 2 ++ inany.c | 1 + ndp.c | 8 ++++++++ 5 files changed, 22 insertions(+), 6 deletions(-) diff --git a/arp.c b/arp.c index 44677ad..90ed5dc 100644 --- a/arp.c +++ b/arp.c @@ -69,6 +69,7 @@ static bool ignore_arp(const struct ctx *c, */ int arp(const struct ctx *c, struct iov_tail *data) { + union inany_addr tgt, tgt_nat; struct { struct ethhdr eh; struct arphdr ah; @@ -102,8 +103,12 @@ int arp(const struct ctx *c, struct iov_tail *data) resp.ah.ar_hln = ah->ar_hln; resp.ah.ar_pln = ah->ar_pln; - /* ARP message */ - memcpy(resp.am.sha, c->our_tap_mac, sizeof(resp.am.sha)); + /* MAC address to return in ARP message */ + inany_from_af(&tgt, AF_INET, am->tip); + fwd_nat_outbound(c, &tgt, &tgt_nat); + fwd_neigh_mac_get(c, &tgt_nat, resp.am.sha); + + /* Rest of ARP message */ memcpy(resp.am.sip, am->tip, sizeof(resp.am.sip)); memcpy(resp.am.tha, am->sha, sizeof(resp.am.tha)); memcpy(resp.am.tip, am->sip, sizeof(resp.am.tip)); diff --git a/fwd.c b/fwd.c index fcd119e..9e4dbb8 100644 --- a/fwd.c +++ b/fwd.c @@ -513,7 +513,7 @@ static bool fwd_guest_accessible(const struct ctx *c, } /** - * nat_outbound() - Apply address translation for outbound (TAP to HOST) + * fwd_nat_outbound() - Apply address translation for outbound (TAP to HOST) * @c: Execution context * @addr: Input address (as seen on TAP interface) * @translated: Output address (as seen on HOST interface) @@ -521,8 +521,8 @@ 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. */ -static void nat_outbound(const struct ctx *c, const union inany_addr *addr, - union inany_addr *translated) +void fwd_nat_outbound(const struct ctx *c, const union inany_addr *addr, + union inany_addr *translated) { if (inany_equals4(addr, &c->ip4.map_host_loopback)) *translated = inany_loopback4; @@ -556,7 +556,7 @@ uint8_t fwd_nat_from_tap(const struct ctx *c, uint8_t proto, inany_equals6(&ini->oaddr, &c->ip6.dns_match)) tgt->eaddr.a6 = c->ip6.dns_host; else - nat_outbound(c, &ini->oaddr, &tgt->eaddr); + fwd_nat_outbound(c, &ini->oaddr, &tgt->eaddr); tgt->eport = ini->oport; diff --git a/fwd.h b/fwd.h index 728601f..a4dd6bb 100644 --- a/fwd.h +++ b/fwd.h @@ -50,6 +50,8 @@ void fwd_scan_ports_init(struct ctx *c); bool nat_inbound(const struct ctx *c, const union inany_addr *addr, union inany_addr *translated); +void fwd_nat_outbound(const struct ctx *c, const union inany_addr *addr, + union inany_addr *translated); uint8_t fwd_nat_from_tap(const struct ctx *c, uint8_t proto, const struct flowside *ini, struct flowside *tgt); uint8_t fwd_nat_from_splice(const struct ctx *c, uint8_t proto, 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 eb090cd..944371c 100644 --- a/ndp.c +++ b/ndp.c @@ -196,6 +196,7 @@ 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, tgt_nat; struct ndp_na na = { .ih = { .icmp6_type = NA, @@ -215,6 +216,13 @@ 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 MAC address if remote host's address or + * NAT translated address can be found in NDP table. + */ + inany_from_af(&tgt, AF_INET6, addr); + fwd_nat_outbound(c, &tgt, &tgt_nat); + fwd_neigh_mac_get(c, &tgt_nat, na.target_l2_addr.mac); + ndp_send(c, dst, &na, sizeof(na)); } -- 2.50.1