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=FAnvAF+M; 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 EDEDB5A0274 for ; Mon, 22 Sep 2025 00:09:18 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1758492556; 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=A45k9LMWZE4fdJynYtQ8qu643z0sMIli4a2giDRsoXU=; b=FAnvAF+MCBNPLMmAMRYJDWhvajUbFEiQYCNPjOS2UpRfKKMFJtYssg6Wg9ViL6UHk3YIih 5odN1JQHKxwXTt3zVEUu6zaad/ta6igh0CPXNQnlHPzfidyXO5ehET4gN6IcZPOOSELzq2 uHXfcWLZWO2crhK2SCnaxbJSCqY5L9c= Received: from mx-prod-mc-04.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-45-OF2tL7LcPQy0tkQtVohpwQ-1; Sun, 21 Sep 2025 18:09:10 -0400 X-MC-Unique: OF2tL7LcPQy0tkQtVohpwQ-1 X-Mimecast-MFC-AGG-ID: OF2tL7LcPQy0tkQtVohpwQ_1758492550 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (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-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0ACB119560AE; Sun, 21 Sep 2025 22:09:10 +0000 (UTC) Received: from jmaloy-thinkpadp16vgen1.rmtcaqc.csb (unknown [10.22.88.62]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 177C830002C5; Sun, 21 Sep 2025 22:09:07 +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 v8 1/8] netlink: add subsciption on changes in NDP/ARP table Date: Sun, 21 Sep 2025 18:08:58 -0400 Message-ID: <20250921220905.478621-2-jmaloy@redhat.com> In-Reply-To: <20250921220905.478621-1-jmaloy@redhat.com> References: <20250921220905.478621-1-jmaloy@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: iS2epsxYG31JSR-EskF3w7J8d49WLM0c5ogk96B9tcs_1758492550 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true Message-ID-Hash: BZTOYT546Q76MLMXUKJXAMS4T3CHYHV6 X-Message-ID-Hash: BZTOYT546Q76MLMXUKJXAMS4T3CHYHV6 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: The solution to bug https://bugs.passt.top/show_bug.cgi?id=120 requires the ability to translate from an IP address to its corresponding MAC address in cases where those are present in the ARP or NDP tables. To keep track of the contents of these tables we add a netlink based neighbour subscription feature. Signed-off-by: Jon Maloy Reviewed-by: David Gibson --- v3: - Added an attribute contianing NDA_DST to sent message, so that we let the kernel do the filtering of the IP address and return only one entry. - Added interface index to the call signature. Since the only interface we know is the template interface, this limits the number of hosts that will be seen as 'network segment local' from a PASST viewpoint. v4: - Made loop independent of attribute order. - Ignoring L2 addresses which are not of size ETH_ALEN. v5: - Changed return value of new function, so caller can know if a MAC address really was found. v6: - Removed warning printout which had ended up in the wrong commit. v8: - Changed to neighbour event subscription model netlink: arp/ndp table subscription --- epoll_type.h | 2 + netlink.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++++++ netlink.h | 4 ++ passt.c | 8 ++++ 4 files changed, 128 insertions(+) diff --git a/epoll_type.h b/epoll_type.h index 12ac59b..a90ffb6 100644 --- a/epoll_type.h +++ b/epoll_type.h @@ -44,6 +44,8 @@ enum epoll_type { EPOLL_TYPE_REPAIR_LISTEN, /* TCP_REPAIR helper socket */ EPOLL_TYPE_REPAIR, + /* Netlink neighbour subscription socket */ + EPOLL_TYPE_NL_NEIGH, EPOLL_NUM_TYPES, }; diff --git a/netlink.c b/netlink.c index c436780..1faf3da 100644 --- a/netlink.c +++ b/netlink.c @@ -53,6 +53,7 @@ int nl_sock = -1; int nl_sock_ns = -1; static int nl_seq = 1; +static int nl_sock_neigh = -1; /** * nl_sock_init_do() - Set up netlink sockets in init or target namespace @@ -84,6 +85,119 @@ static int nl_sock_init_do(void *arg) return 0; } +/** + * nl_neigh_subscr_init() - Open a NETLINK_ROUTE socket and subscribe to neighbor events + * + * Return: 0 on success, -1 on failure + */ +int nl_neigh_subscr_init(struct ctx *c) +{ + struct epoll_event ev = { 0 }; + union epoll_ref ref = { .type = EPOLL_TYPE_NL_NEIGH, .fd = 0 }; + + struct sockaddr_nl addr = { + .nl_family = AF_NETLINK, + .nl_groups = RTMGRP_NEIGH, + }; + + if (nl_sock_neigh >= 0) + return 0; + + nl_sock_neigh = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE); + if (nl_sock_neigh < 0) + return -1; + + if (bind(nl_sock_neigh, (struct sockaddr *)&addr, sizeof(addr)) < 0) { + close(nl_sock_neigh); + nl_sock_neigh = -1; + return -1; + } + + ref.fd = nl_sock_neigh; + ev.events = EPOLLIN; + ev.data.u64 = ref.u64; + if (epoll_ctl(c->epollfd, EPOLL_CTL_ADD, nl_sock_neigh, &ev) == -1) { + close(nl_sock_neigh); + nl_sock_neigh = -1; + return -1; + } + + return 0; +} + +/** + * nl_neigh_subscr_handler() - Non-blocking drain of pending neighbor updates + * @c: Execution context + */ +void nl_neigh_subscr_handler(struct ctx *c) +{ + struct nlmsghdr *nh; + char buf[NLBUFSIZ]; + ssize_t n; + + if (nl_sock_neigh < 0) + return; + + for (;;) { + n = recv(nl_sock_neigh, buf, sizeof(buf), MSG_DONTWAIT); + if (n <= 0) + return; + + nh = (struct nlmsghdr *)buf; + for (; NLMSG_OK(nh, n); nh = NLMSG_NEXT(nh, n)) { + struct ndmsg *ndm = NLMSG_DATA(nh); + struct rtattr *rta = (struct rtattr *)(ndm + 1); + size_t na = NLMSG_PAYLOAD(nh, sizeof(*ndm)); + const uint8_t *lladdr = NULL; + const void *dst = NULL; + size_t lladdr_len = 0; + size_t dstlen = 0; + + if (nh->nlmsg_type == NLMSG_DONE || + nh->nlmsg_type == NLMSG_ERROR) + continue; + + if (nh->nlmsg_type != RTM_NEWNEIGH && + nh->nlmsg_type != RTM_DELNEIGH) + continue; + + for (; RTA_OK(rta, na); rta = RTA_NEXT(rta, na)) { + switch (rta->rta_type) { + case NDA_DST: + dst = RTA_DATA(rta); + dstlen = RTA_PAYLOAD(rta); + break; + case NDA_LLADDR: + lladdr = RTA_DATA(rta); + lladdr_len = RTA_PAYLOAD(rta); + break; + default: + break; + } + } + + if (!dst) + continue; + + if (dstlen != sizeof(struct in_addr) && + dstlen != sizeof(struct in6_addr)) + continue; + + char abuf[INET6_ADDRSTRLEN]; + + if (dstlen == sizeof(struct in_addr)) + inet_ntop(AF_INET, dst, abuf, sizeof(abuf)); + else + inet_ntop(AF_INET6, dst, abuf, sizeof(abuf)); + + if (nh->nlmsg_type == RTM_NEWNEIGH) + debug("neigh: NEW %s lladdr_len=%zu", abuf, lladdr_len); + else + debug("neigh: DEL %s", abuf); + } + } +} + /** * nl_sock_init() - Call nl_sock_init_do(), won't return on failure * @c: Execution context diff --git a/netlink.h b/netlink.h index b51e99c..a7d3506 100644 --- a/netlink.h +++ b/netlink.h @@ -17,6 +17,8 @@ int nl_route_dup(int s_src, unsigned int ifi_src, int s_dst, unsigned int ifi_dst, sa_family_t af); int nl_addr_get(int s, unsigned int ifi, sa_family_t af, void *addr, int *prefix_len, void *addr_l); +bool nl_neigh_mac_get(int s, const union inany_addr *addr, int ifi, + unsigned char *mac); int nl_addr_set(int s, unsigned int ifi, sa_family_t af, const void *addr, int prefix_len); int nl_addr_get_ll(int s, unsigned int ifi, struct in6_addr *addr); @@ -28,5 +30,7 @@ int nl_link_set_mac(int s, unsigned int ifi, const void *mac); int nl_link_set_mtu(int s, unsigned int ifi, int mtu); int nl_link_set_flags(int s, unsigned int ifi, unsigned int set, unsigned int change); +int nl_neigh_subscr_init(struct ctx *c); +void nl_neigh_subscr_handler(struct ctx *c); #endif /* NETLINK_H */ diff --git a/passt.c b/passt.c index 31fbb75..e20bbad 100644 --- a/passt.c +++ b/passt.c @@ -53,6 +53,7 @@ #include "vu_common.h" #include "migrate.h" #include "repair.h" +#include "netlink.h" #define EPOLL_EVENTS 8 @@ -79,6 +80,7 @@ char *epoll_type_str[] = { [EPOLL_TYPE_VHOST_KICK] = "vhost-user kick socket", [EPOLL_TYPE_REPAIR_LISTEN] = "TCP_REPAIR helper listening socket", [EPOLL_TYPE_REPAIR] = "TCP_REPAIR helper socket", + [EPOLL_TYPE_NL_NEIGH] = "netlink neighbour subscription socket", }; static_assert(ARRAY_SIZE(epoll_type_str) == EPOLL_NUM_TYPES, "epoll_type_str[] doesn't match enum epoll_type"); @@ -322,6 +324,9 @@ int main(int argc, char **argv) pcap_init(&c); + if (nl_neigh_subscr_init(&c) < 0) + warn("Failed to subscribe to RTMGRP_NEIGH"); + if (!c.foreground) { if ((devnull_fd = open("/dev/null", O_RDWR | O_CLOEXEC)) < 0) die_perror("Failed to open /dev/null"); @@ -414,6 +419,9 @@ loop: case EPOLL_TYPE_REPAIR: repair_handler(&c, eventmask); break; + case EPOLL_TYPE_NL_NEIGH: + nl_neigh_subscr_handler(&c); + break; default: /* Can't happen */ ASSERT(0); -- 2.50.1