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Miller" , David Ahern , Donald Hunter , Eric Dumazet , Ido Schimmel , Jacob Keller , Jakub Kicinski , Kuniyuki Iwashima , Nicolas Dichtel , Nikolaos Gkarlis , Paolo Abeni , Sabrina Dubroca , Shuah Khan , Simon Horman , Stanislav Fomichev , Willem de Bruijn , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH net-next v8 3/5] net: add AF_PACKET multicast dumps Date: Sun, 27 Sep 2026 09:24:25 +0900 Message-ID: <20260927002427.4519-4-sigefriedhyy@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260927002427.4519-1-sigefriedhyy@gmail.com> References: <20260927002427.4519-1-sigefriedhyy@gmail.com> Precedence: bulk X-Mailing-List: linux-kselftest@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 next to the dev->mc helpers in dev_addr_lists.c 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_GLOBAL in IFA_FLAGS reports netdev_hw_addr::global_use, set by dev_mc_add_global() (SIOCADDMULTI) and dev_mc_add_excl() ("bridge fdb add ... self"), i.e. entries added explicitly rather than by a protocol join. This is the static column of /proc/net/dev_mcast - ifa_scope is RT_SCOPE_LINK This covers every column of /proc/net/dev_mcast. AF_PACKET is the family iproute2 already uses for link-layer addresses ("ip -0"). The default FDB dump also walks dev->mc, but only for Ethernet devices without an ndo_fdb_dump of their own, so bridge, vxlan or macvlan devices never show their multicast filter there, and it has no users count or global_use bit. Extending it would change "bridge fdb show" output and add NDA_* attributes. Requests are always validated, there are no legacy users: prefixlen, flags and scope must be zero, ifa_index selects one device and IFA_TARGET_NETNSID is the only attribute accepted. The dump runs under RCU and netif_addr_lock_bh() without RTNL. cb->seq is sampled from the dev->mc generation counter and dev_base_seq under the address lock of each device and again when a round ends, so a change since the previous device or dump round sets NLM_F_DUMP_INTR, also when the last round dumps nothing because the device it stopped at is gone. Signed-off-by: Yuyang Huang Reviewed-by: Nicolas Dichtel --- include/linux/netdevice.h | 1 + include/uapi/linux/if_addr.h | 1 + net/core/dev_addr_lists.c | 195 +++++++++++++++++++++++++++++++++++ net/core/rtnetlink.c | 2 + 4 files changed, 199 insertions(+) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 69d1cde0a38a..75c94ecc1322 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -5167,6 +5167,7 @@ int dev_mc_sync_multiple(struct net_device *to, struct net_device *from); void dev_mc_unsync(struct net_device *to, struct net_device *from); void dev_mc_flush(struct net_device *dev); void dev_mc_init(struct net_device *dev); +int dev_mc_dump(struct sk_buff *skb, struct netlink_callback *cb); /** * __dev_mc_sync - Synchronize device's multicast list diff --git a/include/uapi/linux/if_addr.h b/include/uapi/linux/if_addr.h index 7fb630b7fe31..0a1ad9ebb47b 100644 --- a/include/uapi/linux/if_addr.h +++ b/include/uapi/linux/if_addr.h @@ -57,6 +57,7 @@ enum { #define IFA_F_NOPREFIXROUTE 0x200 #define IFA_F_MCAUTOJOIN 0x400 #define IFA_F_STABLE_PRIVACY 0x800 +#define IFA_F_GLOBAL 0x1000 struct ifa_cacheinfo { __u32 ifa_prefered; diff --git a/net/core/dev_addr_lists.c b/net/core/dev_addr_lists.c index c941c3ec1007..806a694a996d 100644 --- a/net/core/dev_addr_lists.c +++ b/net/core/dev_addr_lists.c @@ -10,8 +10,12 @@ #include #include #include +#include #include #include +#include +#include +#include #include #include "dev.h" @@ -1215,6 +1219,197 @@ void dev_mc_init(struct net_device *dev) } EXPORT_SYMBOL(dev_mc_init); +static int dev_mc_fill_addr(struct sk_buff *skb, const struct net_device *dev, + const struct netdev_hw_addr *ha, u32 portid, + u32 seq, unsigned int flags, int netnsid) +{ + u32 ifa_flags = ha->global_use ? IFA_F_GLOBAL : 0; + 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 holds 8 bits, the full value is in IFA_FLAGS */ + ifm->ifa_flags = (__u8)ifa_flags; + ifm->ifa_scope = RT_SCOPE_LINK; + ifm->ifa_index = dev->ifindex; + + if ((netnsid >= 0 && + nla_put_s32(skb, IFA_TARGET_NETNSID, netnsid)) || + nla_put(skb, IFA_MULTICAST, dev->addr_len, ha->addr) || + nla_put_u32(skb, IFA_MC_USERS, ha->refcount) || + nla_put_u32(skb, IFA_FLAGS, ifa_flags)) { + nlmsg_cancel(skb, nlh); + return -EMSGSIZE; + } + + nlmsg_end(skb, nlh); + return 0; +} + +/* Combine dev_mc_genid and dev_base_seq to detect changes, like + * inet_base_seq(). + */ +static u32 dev_mc_base_seq(const struct net *net) +{ + u32 res = atomic_read(&net->dev_mc_genid) + + READ_ONCE(net->dev_base_seq); + + /* Must not return 0 (see nl_dump_check_consistent()). */ + if (!res) + res = 0x80000000; + return res; +} + +static int dev_mc_dump_dev(struct net_device *dev, struct sk_buff *skb, + struct netlink_callback *cb, int *s_addr_idx, + unsigned int flags, int netnsid) +{ + struct netdev_hw_addr *ha; + int addr_idx = 0; + int err = 0; + + netif_addr_lock_bh(dev); + /* Sampled under the lock, see nl_dump_check_consistent() */ + cb->seq = dev_mc_base_seq(dev_net(dev)); + netdev_for_each_mc_addr(ha, dev) { + if (addr_idx < *s_addr_idx) { + addr_idx++; + continue; + } + err = dev_mc_fill_addr(skb, dev, ha, NETLINK_CB(cb->skb).portid, + cb->nlh->nlmsg_seq, flags, netnsid); + if (err < 0) + break; + nl_dump_check_consistent(cb, nlmsg_hdr(skb)); + addr_idx++; + } + netif_addr_unlock_bh(dev); + + *s_addr_idx = err < 0 ? addr_idx : 0; + + return err; +} + +struct dev_mc_dump_filter { + struct net *tgt_net; + netns_tracker ns_tracker; + int netnsid; + int ifindex; +}; + +static const struct nla_policy dev_mc_dump_policy[IFA_MAX + 1] = { + [IFA_TARGET_NETNSID] = { .type = NLA_S32 }, +}; + +static int dev_mc_valid_dump_req(const struct nlmsghdr *nlh, struct sock *sk, + struct dev_mc_dump_filter *filter, + struct netlink_ext_ack *extack) +{ + struct nlattr *tb[IFA_MAX + 1]; + struct ifaddrmsg *ifm; + int err; + + 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; + } + + err = nlmsg_parse(nlh, sizeof(*ifm), tb, IFA_MAX, + dev_mc_dump_policy, extack); + if (err < 0) + return err; + + if (tb[IFA_TARGET_NETNSID]) { + struct net *net; + + filter->netnsid = nla_get_s32(tb[IFA_TARGET_NETNSID]); + net = rtnl_get_net_ns_capable(sk, filter->netnsid); + if (IS_ERR(net)) { + NL_SET_ERR_MSG(extack, + "Invalid target network namespace id"); + return PTR_ERR(net); + } + netns_tracker_alloc(net, &filter->ns_tracker, GFP_KERNEL); + filter->tgt_net = net; + } + + filter->ifindex = ifm->ifa_index; + + return 0; +} + +int dev_mc_dump(struct sk_buff *skb, struct netlink_callback *cb) +{ + struct dev_mc_dump_filter filter = { + .tgt_net = sock_net(skb->sk), + .netnsid = -1, + }; + unsigned int flags = NLM_F_MULTI; + struct { + unsigned long ifindex; + int addr_idx; + } *ctx = (void *)cb->ctx; + unsigned long s_ifindex; + struct net_device *dev; + int err; + + err = dev_mc_valid_dump_req(cb->nlh, skb->sk, &filter, cb->extack); + if (err < 0) + return err; + + rcu_read_lock(); + + if (filter.ifindex) { + cb->answer_flags |= NLM_F_DUMP_FILTERED; + flags |= NLM_F_DUMP_FILTERED; + dev = dev_get_by_index_rcu(filter.tgt_net, filter.ifindex); + if (!dev) { + err = -ENODEV; + goto out; + } + err = dev_mc_dump_dev(dev, skb, cb, &ctx->addr_idx, flags, + filter.netnsid); + goto out; + } + + s_ifindex = ctx->ifindex; + for_each_netdev_dump(filter.tgt_net, dev, ctx->ifindex) { + /* The device the dump stopped at is gone, do not skip + * entries of the next one. + */ + if (dev->ifindex != s_ifindex) + ctx->addr_idx = 0; + err = dev_mc_dump_dev(dev, skb, cb, &ctx->addr_idx, flags, + filter.netnsid); + if (err < 0) + break; + } +out: + /* A round that dumps no device, e.g. the one it stopped at is gone, + * still needs the NLMSG_DONE check to see the change. + */ + cb->seq = dev_mc_base_seq(filter.tgt_net); + rcu_read_unlock(); + if (filter.netnsid >= 0) + put_net_track(filter.tgt_net, &filter.ns_tracker); + return err; +} + static int netif_addr_lists_snapshot(struct net_device *dev, struct netdev_hw_addr_list *uc_snap, struct netdev_hw_addr_list *mc_snap, diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index e3444fd24061..204dc9040e3c 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -7278,6 +7278,8 @@ 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 = dev_mc_dump, .flags = RTNL_FLAG_DUMP_UNLOCKED}, {.protocol = PF_BRIDGE, .msgtype = RTM_GETLINK, .dumpit = rtnl_bridge_getlink}, {.protocol = PF_BRIDGE, .msgtype = RTM_DELLINK, -- 2.43.0