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Miller" , David Ahern , Donald Hunter , Eric Dumazet , Ido Schimmel , Jakub Kicinski , Kuniyuki Iwashima , Nikolaos Gkarlis , Paolo Abeni , Sabrina Dubroca , Shuah Khan , Simon Horman , Stanislav Fomichev , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH net-next 1/3] rtnetlink: add AF_PACKET multicast dumps Date: Sat, 5 Sep 2026 18:39:30 +0900 Message-ID: <20260905093932.43726-2-sigefriedhyy@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260905093932.43726-1-sigefriedhyy@gmail.com> References: <20260905093932.43726-1-sigefriedhyy@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" RTM_GETMULTICAST dumps IPv4 and IPv6 multicast group memberships, but the device multicast list (dev->mc) is only available through /proc/net/dev_mcast, so "ip maddr show" still has to parse procfs for its link-layer entries. Handle RTM_GETMULTICAST dumps with ifa_family set to AF_PACKET and report every entry of dev->mc in the existing ifaddrmsg format: - IFA_MULTICAST carries the raw link-layer address - IFA_MC_USERS carries the entry reference count - IFA_F_PERMANENT marks entries added with SIOCADDMULTI (netdev_hw_addr::global_use, "static" in "ip maddr") - ifa_scope is RT_SCOPE_LINK This covers every column of /proc/net/dev_mcast. Strict requests are validated like the IPv4 dump, except that no attributes are accepted; a non-zero ifa_index restricts the dump to that device. The dump runs under RCU and netif_addr_lock_bh() and does not need RTNL. Signed-off-by: Yuyang Huang --- net/core/rtnetlink.c | 132 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 132 insertions(+) diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index 81c5a6104dea..5e83232c1504 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -4566,6 +4566,136 @@ static int rtnl_dump_all(struct sk_buff *skb, struc= t netlink_callback *cb) return skb->len ? : ret; } =20 +static int rtnl_fill_mcaddr(struct sk_buff *skb, const struct net_device *= dev, + const struct netdev_hw_addr *ha, u32 portid, + u32 seq, unsigned int flags) +{ + struct ifaddrmsg *ifm; + struct nlmsghdr *nlh; + + nlh =3D nlmsg_put(skb, portid, seq, RTM_GETMULTICAST, sizeof(*ifm), + flags); + if (!nlh) + return -EMSGSIZE; + + ifm =3D nlmsg_data(nlh); + ifm->ifa_family =3D AF_PACKET; + ifm->ifa_prefixlen =3D 0; + ifm->ifa_flags =3D ha->global_use ? IFA_F_PERMANENT : 0; + ifm->ifa_scope =3D RT_SCOPE_LINK; + ifm->ifa_index =3D dev->ifindex; + + if (nla_put(skb, IFA_MULTICAST, dev->addr_len, ha->addr) || + nla_put_u32(skb, IFA_MC_USERS, ha->refcount)) { + nlmsg_cancel(skb, nlh); + return -EMSGSIZE; + } + + nlmsg_end(skb, nlh); + return 0; +} + +static int rtnl_dump_mcaddr_dev(struct net_device *dev, struct sk_buff *sk= b, + struct netlink_callback *cb, int *s_addr_idx, + unsigned int flags) +{ + struct netdev_hw_addr *ha; + int addr_idx =3D 0; + int err =3D 0; + + netif_addr_lock_bh(dev); + netdev_for_each_mc_addr(ha, dev) { + if (addr_idx < *s_addr_idx) { + addr_idx++; + continue; + } + err =3D rtnl_fill_mcaddr(skb, dev, ha, NETLINK_CB(cb->skb).portid, + cb->nlh->nlmsg_seq, flags); + if (err < 0) + break; + addr_idx++; + } + netif_addr_unlock_bh(dev); + + *s_addr_idx =3D err < 0 ? addr_idx : 0; + + return err; +} + +static int rtnl_valid_dump_mcaddr_req(const struct nlmsghdr *nlh, + struct netlink_ext_ack *extack, + int *pifindex) +{ + struct ifaddrmsg *ifm; + + ifm =3D nlmsg_payload(nlh, sizeof(*ifm)); + if (!ifm) { + NL_SET_ERR_MSG(extack, + "Invalid header for multicast dump request"); + return -EINVAL; + } + + if (ifm->ifa_prefixlen || ifm->ifa_flags || ifm->ifa_scope) { + NL_SET_ERR_MSG(extack, + "Invalid values in multicast dump header"); + return -EINVAL; + } + + if (nlmsg_attrlen(nlh, sizeof(*ifm))) { + NL_SET_ERR_MSG(extack, + "Invalid data after multicast dump header"); + return -EINVAL; + } + + *pifindex =3D ifm->ifa_index; + + return 0; +} + +static int rtnl_dump_mcaddr(struct sk_buff *skb, struct netlink_callback *= cb) +{ + struct net *net =3D sock_net(skb->sk); + unsigned int flags =3D NLM_F_MULTI; + struct { + unsigned long ifindex; + int addr_idx; + } *ctx =3D (void *)cb->ctx; + struct net_device *dev; + int ifindex =3D 0; + int err =3D 0; + + if (cb->strict_check) { + err =3D rtnl_valid_dump_mcaddr_req(cb->nlh, cb->extack, + &ifindex); + if (err < 0) + return err; + } + + rcu_read_lock(); + + if (ifindex) { + cb->answer_flags |=3D NLM_F_DUMP_FILTERED; + flags |=3D NLM_F_DUMP_FILTERED; + dev =3D dev_get_by_index_rcu(net, ifindex); + if (!dev) { + err =3D -ENODEV; + goto out; + } + err =3D rtnl_dump_mcaddr_dev(dev, skb, cb, &ctx->addr_idx, flags); + goto out; + } + + for_each_netdev_dump(net, dev, ctx->ifindex) { + err =3D rtnl_dump_mcaddr_dev(dev, skb, cb, &ctx->addr_idx, + flags); + if (err < 0) + break; + } +out: + rcu_read_unlock(); + return err; +} + struct sk_buff *rtmsg_ifinfo_build_skb(int type, struct net_device *dev, unsigned int change, u32 event, gfp_t flags, int *new_nsid, @@ -7251,6 +7381,8 @@ static const struct rtnl_msg_handler rtnetlink_rtnl_m= sg_handlers[] __initconst =3D {.msgtype =3D RTM_SETSTATS, .doit =3D rtnl_stats_set}, {.msgtype =3D RTM_NEWLINKPROP, .doit =3D rtnl_newlinkprop}, {.msgtype =3D RTM_DELLINKPROP, .doit =3D rtnl_dellinkprop}, + {.protocol =3D PF_PACKET, .msgtype =3D RTM_GETMULTICAST, + .dumpit =3D rtnl_dump_mcaddr, .flags =3D RTNL_FLAG_DUMP_UNLOCKED}, {.protocol =3D PF_BRIDGE, .msgtype =3D RTM_GETLINK, .dumpit =3D rtnl_bridge_getlink}, {.protocol =3D PF_BRIDGE, .msgtype =3D RTM_DELLINK, --=20 2.43.0 From nobody Sat Sep 26 03:52:01 2026 Received: from mail-pl1-f180.google.com (mail-pl1-f180.google.com [209.85.214.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C4F343CFF73 for ; 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Sat, 05 Sep 2026 02:39:49 -0700 (PDT) Received: from m-upc-A520M-HDV.lan ([2400:2410:3f60:500:dbc1:ef89:4dd5:b812]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2db1495a0c0sm20393745ad.17.2026.09.05.02.39.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 05 Sep 2026 02:39:48 -0700 (PDT) Sender: Yuyang Huang From: Yuyang Huang To: Yuyang Huang Cc: "David S. Miller" , David Ahern , Donald Hunter , Eric Dumazet , Ido Schimmel , Jakub Kicinski , Kuniyuki Iwashima , Nikolaos Gkarlis , Paolo Abeni , Sabrina Dubroca , Shuah Khan , Simon Horman , Stanislav Fomichev , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH net-next 2/3] netlink: specs: rt-addr: document AF_PACKET multicast dumps Date: Sat, 5 Sep 2026 18:39:31 +0900 Message-ID: <20260905093932.43726-3-sigefriedhyy@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260905093932.43726-1-sigefriedhyy@gmail.com> References: <20260905093932.43726-1-sigefriedhyy@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Mention that ifa-family AF_PACKET dumps link-layer multicast addresses and what the permanent flag means for them. Signed-off-by: Yuyang Huang --- Documentation/netlink/specs/rt-addr.yaml | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/Documentation/netlink/specs/rt-addr.yaml b/Documentation/netli= nk/specs/rt-addr.yaml index 0ecbd24c890c..2a2310cb0df0 100644 --- a/Documentation/netlink/specs/rt-addr.yaml +++ b/Documentation/netlink/specs/rt-addr.yaml @@ -168,7 +168,12 @@ operations: attributes: *ifaddr-all - name: getmulticast - doc: Get / dump IPv4/IPv6 multicast addresses. + doc: | + Get / dump multicast addresses. ifa-family selects the address + family: AF_INET or AF_INET6 for the IP multicast groups joined on + a device, AF_PACKET for the link-layer multicast addresses in the + device filter. 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Miller" , David Ahern , Donald Hunter , Eric Dumazet , Ido Schimmel , Jakub Kicinski , Kuniyuki Iwashima , Nikolaos Gkarlis , Paolo Abeni , Sabrina Dubroca , Shuah Khan , Simon Horman , Stanislav Fomichev , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH net-next 3/3] selftests: net: test AF_PACKET multicast dumps Date: Sat, 5 Sep 2026 18:39:32 +0900 Message-ID: <20260905093932.43726-4-sigefriedhyy@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260905093932.43726-1-sigefriedhyy@gmail.com> References: <20260905093932.43726-1-sigefriedhyy@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Dump the link-layer multicast addresses of a dummy device and verify that ifa_index restricts the dump to that device, that the all-hosts address joined on link up is listed without IFA_F_PERMANENT and that an address added with SIOCADDMULTI is listed with IFA_F_PERMANENT and IFA_MC_USERS. Skip when the kernel does not support AF_PACKET dumps. Signed-off-by: Yuyang Huang --- tools/testing/selftests/net/rtnetlink.py | 58 ++++++++++++++++++++++-- 1 file changed, 55 insertions(+), 3 deletions(-) diff --git a/tools/testing/selftests/net/rtnetlink.py b/tools/testing/selft= ests/net/rtnetlink.py index 5cc3ebdcf08d..94340dac0e21 100755 --- a/tools/testing/selftests/net/rtnetlink.py +++ b/tools/testing/selftests/net/rtnetlink.py @@ -1,17 +1,21 @@ #!/usr/bin/env python3 # SPDX-License-Identifier: GPL-2.0 =20 +import errno import socket import struct import time from lib.py import bkg, ip, ksft_exit, ksft_run, ksft_eq, ksft_ge, ksft_tr= ue, KsftSkipEx -from lib.py import ksft_not_in, ksft_not_none -from lib.py import CmdExitFailure, NetNS, NetNSEnter, RtnlAddrFamily, Rtnl= RouteFamily +from lib.py import ksft_in, ksft_not_in, ksft_not_none +from lib.py import CmdExitFailure, NetNS, NetNSEnter, NlError, RtnlAddrFam= ily, RtnlRouteFamily from lib.py import defer =20 IPV4_ALL_HOSTS_MULTICAST =3D b'\xe0\x00\x00\x01' IPV4_TEST_MULTICAST =3D b'\xef\x01\x01\x01' IPV6_TEST_MULTICAST =3D bytes.fromhex('ff020000000000000000000000000123') +ETH_ALL_HOSTS_MULTICAST =3D bytes.fromhex('01005e000001') +ETH_TEST_MULTICAST_STR =3D '01:00:5e:01:01:01' +ETH_TEST_MULTICAST =3D bytes.fromhex(ETH_TEST_MULTICAST_STR.replace(':', '= ')) =20 =20 def _users_for(rtnl: RtnlAddrFamily, family: int, grp: bytes, ifindex: int= ): @@ -105,6 +109,53 @@ def dump_mcaddr6_check() -> None: s2.close() =20 =20 +def dump_mcaddr_l2_check() -> None: + """ + Verify link-layer multicast addresses in an AF_PACKET RTM_GETMULTICAST + dump: the ifa-index filter, mc-users and the permanent flag. + """ + + with NetNS() as ns: + with NetNSEnter(str(ns)): + for ifname in ("dummy1", "dummy2"): + ip(f"link add name {ifname} type dummy") + ip(f"link set {ifname} up") + dev_idx =3D socket.if_nametoindex("dummy1") + ip(f"maddr add {ETH_TEST_MULTICAST_STR} dev dummy1") + + rtnl =3D RtnlAddrFamily() + try: + addresses =3D rtnl.getmulticast( + {"ifa-family": socket.AF_PACKET, "ifa-index": dev_idx}, + dump=3DTrue) + except NlError as e: + if e.error =3D=3D errno.EOPNOTSUPP: + raise KsftSkipEx( + "kernel does not support AF_PACKET multicast dump") + raise + + # dummy2 has entries as well, only dummy1 may be listed + ksft_eq({addr['ifa-index'] for addr in addresses}, {dev_idx}, + "AF_PACKET multicast dump ignored ifa-index filter") + + entries =3D {addr['multicast']: addr for addr in addresses} + + # Bringing an Ethernet device up joins 224.0.0.1, which maps + # to 01:00:5e:00:00:01 in the device multicast list. + ksft_in(ETH_ALL_HOSTS_MULTICAST, entries, + "dummy1 does not have the all-hosts link-layer address= ") + ksft_not_in('permanent', + entries[ETH_ALL_HOSTS_MULTICAST]['ifa-flags'], + "protocol entry is permanent") + + ksft_in(ETH_TEST_MULTICAST, entries, + "dummy1 does not have the SIOCADDMULTI address") + ksft_eq(entries[ETH_TEST_MULTICAST]['mc-users'], 1, + "unexpected mc-users for the SIOCADDMULTI address") + ksft_in('permanent', entries[ETH_TEST_MULTICAST]['ifa-flags'], + "SIOCADDMULTI entry is not permanent") + + def ipv4_devconf_notify() -> None: """ Configure an interface and set ipv4-devconf values through netlink @@ -315,7 +366,8 @@ def ipv6_route_del_reason_absent() -> None: =20 =20 def main() -> None: - ksft_run([dump_mcaddr_check, dump_mcaddr6_check, ipv4_devconf_notify, + ksft_run([dump_mcaddr_check, dump_mcaddr6_check, dump_mcaddr_l2_check, + ipv4_devconf_notify, ipv6_route_del_reason_expired, ipv6_route_del_reason_ra_withdrawn, ipv6_route_del_reason_absent]) --=20 2.43.0