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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: 8bit 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, struct netlink_callback *cb) return skb->len ? : ret; } +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 = nlmsg_put(skb, portid, seq, RTM_GETMULTICAST, sizeof(*ifm), + flags); + if (!nlh) + return -EMSGSIZE; + + ifm = nlmsg_data(nlh); + ifm->ifa_family = AF_PACKET; + ifm->ifa_prefixlen = 0; + ifm->ifa_flags = ha->global_use ? IFA_F_PERMANENT : 0; + ifm->ifa_scope = RT_SCOPE_LINK; + ifm->ifa_index = 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 *skb, + struct netlink_callback *cb, int *s_addr_idx, + unsigned int flags) +{ + struct netdev_hw_addr *ha; + int addr_idx = 0; + int err = 0; + + netif_addr_lock_bh(dev); + netdev_for_each_mc_addr(ha, dev) { + if (addr_idx < *s_addr_idx) { + addr_idx++; + continue; + } + err = 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 = 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 = 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 = ifm->ifa_index; + + return 0; +} + +static int rtnl_dump_mcaddr(struct sk_buff *skb, struct netlink_callback *cb) +{ + struct net *net = sock_net(skb->sk); + unsigned int flags = NLM_F_MULTI; + struct { + unsigned long ifindex; + int addr_idx; + } *ctx = (void *)cb->ctx; + struct net_device *dev; + int ifindex = 0; + int err = 0; + + if (cb->strict_check) { + err = rtnl_valid_dump_mcaddr_req(cb->nlh, cb->extack, + &ifindex); + if (err < 0) + return err; + } + + rcu_read_lock(); + + if (ifindex) { + cb->answer_flags |= NLM_F_DUMP_FILTERED; + flags |= NLM_F_DUMP_FILTERED; + dev = dev_get_by_index_rcu(net, ifindex); + if (!dev) { + err = -ENODEV; + goto out; + } + err = rtnl_dump_mcaddr_dev(dev, skb, cb, &ctx->addr_idx, flags); + goto out; + } + + for_each_netdev_dump(net, dev, ctx->ifindex) { + err = 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_msg_handlers[] __initconst = {.msgtype = RTM_SETSTATS, .doit = rtnl_stats_set}, {.msgtype = RTM_NEWLINKPROP, .doit = rtnl_newlinkprop}, {.msgtype = RTM_DELLINKPROP, .doit = rtnl_dellinkprop}, + {.protocol = PF_PACKET, .msgtype = RTM_GETMULTICAST, + .dumpit = rtnl_dump_mcaddr, .flags = RTNL_FLAG_DUMP_UNLOCKED}, {.protocol = PF_BRIDGE, .msgtype = RTM_GETLINK, .dumpit = rtnl_bridge_getlink}, {.protocol = PF_BRIDGE, .msgtype = RTM_DELLINK, -- 2.43.0