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=QEjYHORm; 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 C72605A027B for ; Sat, 06 Sep 2025 04:12:07 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1757124726; 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=ILTBESNxP5IvojWzotVOdeeWYiRYj0Ns+UHQ3K7togs=; b=QEjYHORmBT3jL03hFCvMDv8NqQq0QOafH15+Ivbx2DeZsDcxWU2bKWXgwuaj6l00aXRiK1 xYoGQPlixg2NK8yys/TybYyDpuoA4oYNmRj6nQ5Bj5glNSNJMvXKQ8vrLLLZ1RJgNUgmLi eHuV6ye9fyGZnH3pp9tLYHiwvp/w6N8= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-681-YQPbRZijOxWa03k6pKoJ1A-1; Fri, 05 Sep 2025 22:12:05 -0400 X-MC-Unique: YQPbRZijOxWa03k6pKoJ1A-1 X-Mimecast-MFC-AGG-ID: YQPbRZijOxWa03k6pKoJ1A_1757124724 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5BAEF1800447; Sat, 6 Sep 2025 02:12:04 +0000 (UTC) Received: from jmaloy-thinkpadp16vgen1.rmtcaqc.csb (unknown [10.22.88.21]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 0874B180044F; Sat, 6 Sep 2025 02:12:02 +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 v5 04/10] arp/ndp: respond with true MAC address of LAN local remote hosts Date: Fri, 5 Sep 2025 22:11:48 -0400 Message-ID: <20250906021154.2760611-5-jmaloy@redhat.com> In-Reply-To: <20250906021154.2760611-1-jmaloy@redhat.com> References: <20250906021154.2760611-1-jmaloy@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: _zKZMjuFYZMeqswSAfIXwyAvVIbTLfwNpnrP2H3zSIg_1757124724 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true Message-ID-Hash: R6C7KL7YLJJSAYNYPP5XTZRPNBS7H6FD X-Message-ID-Hash: R6C7KL7YLJJSAYNYPP5XTZRPNBS7H6FD 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 --- 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. --- arp.c | 9 ++++++++- fwd.c | 5 +++-- fwd.h | 2 ++ inany.c | 1 + ndp.c | 8 ++++++++ 5 files changed, 22 insertions(+), 3 deletions(-) diff --git a/arp.c b/arp.c index 44677ad..8bff505 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; @@ -80,6 +81,7 @@ int arp(const struct ctx *c, struct iov_tail *data) const struct ethhdr *eh; const struct arphdr *ah; const struct arpmsg *am; + uint8_t omac[ETH_ALEN]; eh = IOV_REMOVE_HEADER(data, eh_storage); ah = IOV_REMOVE_HEADER(data, ah_storage); @@ -102,8 +104,13 @@ int arp(const struct ctx *c, struct iov_tail *data) resp.ah.ar_hln = ah->ar_hln; resp.ah.ar_pln = ah->ar_pln; + /* MAC address to return */ + inany_from_af(&tgt, AF_INET, am->tip); + nat_outbound(c, &tgt, &tgt_nat); + fwd_neigh_mac_get(c, &tgt_nat, omac); + /* ARP message */ - memcpy(resp.am.sha, c->our_tap_mac, sizeof(resp.am.sha)); + memcpy(resp.am.sha, omac, sizeof(resp.am.sha)); 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 ab49dba..664e167 100644 --- a/fwd.c +++ b/fwd.c @@ -630,8 +630,8 @@ 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 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; @@ -643,6 +643,7 @@ static void nat_outbound(const struct ctx *c, const union inany_addr *addr, translated->a6 = c->ip6.addr; else *translated = *addr; + } /** diff --git a/fwd.h b/fwd.h index 80da4b1..bf1705b 100644 --- a/fwd.h +++ b/fwd.h @@ -57,6 +57,8 @@ 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 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..820c556 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); + 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