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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Yuyang Huang , Nicolas Dichtel , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, 1342116488@qq.com Subject: Re: [PATCH net-next v2] ipv4: igmp: report IFA_TARGET_NETNSID in multicast address dumps Message-ID: References: <20261112082352.152338-1-sunwenbo@cmss.chinamobile.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261112082352.152338-1-sunwenbo@cmss.chinamobile.com> On Thu, Nov 12, 2026 at 04:23:52PM +0800, Wenbo Sun wrote: > Commit eb4e17a1d915 ("netlink: support dumping IPv4 multicast addresses") > extended RTM_GETMULTICAST to dump IPv4 multicast addresses by reusing > inet_valid_dump_ifaddr_req(), which already accepts IFA_TARGET_NETNSID > and switches to the target network namespace. However, > inet_fill_ifmcaddr() does not include IFA_TARGET_NETNSID in the dump > replies yet. > > In contrast, IPv4 unicast dumps (inet_fill_ifaddr()), IPv6 multicast > dumps (inet6_fill_ifmcaddr()), and AF_PACKET multicast dumps > (dev_mc_fill_addr()) all report IFA_TARGET_NETNSID when a netns id is > specified. Adding the same behavior to IPv4 multicast dumps aligns > reporting across address families and helps userspace consistently > identify target-netns replies. > > Emit IFA_TARGET_NETNSID in inet_fill_ifmcaddr() when args->netnsid >= 0, > and initialize fillargs.netnsid = -1 in inet_ifmcaddr_notify() so that > multicast join/leave notifications do not include IFA_TARGET_NETNSID or > exceed their preallocated skb size. > > This alignment was identified with the assistance of an LLM-based code > review tool, confirmed in a User-Mode Linux (UML) environment where AF_INET > RTM_GETMULTICAST dumps with IFA_TARGET_NETNSID omitted the attribute while > AF_INET6 included it, and verified in UML that AF_INET multicast dumps > now report IFA_TARGET_NETNSID, regular dumps without netnsid continue to > work, and multicast join/leave notifications succeed without warning. > > Signed-off-by: Wenbo Sun > --- > Changes in v2: > - Target net-next as an enhancement/alignment change and drop the Fixes > tag, per Hangbin Liu's review. > - Soften and clarify the commit message to reflect feature alignment with > inet_fill_ifaddr(), inet6_fill_ifmcaddr(), and dev_mc_fill_addr(). > - Link to v1: https://lore.kernel.org/r/20261111082222.327963-1-sunwenbo@cmss.chinamobile.com > > net/ipv4/igmp.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c > index 144fca158adc..831d003677ba 100644 > --- a/net/ipv4/igmp.c > +++ b/net/ipv4/igmp.c > @@ -1517,6 +1517,12 @@ int inet_fill_ifmcaddr(struct sk_buff *skb, struct net_device *dev, > ifm->ifa_scope = RT_SCOPE_UNIVERSE; > ifm->ifa_index = dev->ifindex; > > + if (args->netnsid >= 0 && > + nla_put_s32(skb, IFA_TARGET_NETNSID, args->netnsid)) { > + nlmsg_cancel(skb, nlh); > + return -EMSGSIZE; > + } > + > ci.cstamp = (READ_ONCE(im->mca_cstamp) - INITIAL_JIFFIES) * 100UL / HZ; > ci.tstamp = ci.cstamp; > ci.ifa_prefered = INFINITY_LIFE_TIME; > @@ -1538,6 +1544,7 @@ static void inet_ifmcaddr_notify(struct net_device *dev, > { > struct inet_fill_args fillargs = { > .event = event, > + .netnsid = -1, > }; > struct net *net = dev_net(dev); > struct sk_buff *skb; > -- > 2.33.0 > Reviewed-by: Hangbin Liu