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Message-ID: <CAJieiUgopvmN5VVntPwffP5YmVZGFsWJvafSSXj83DVBVA61uQ@mail.gmail.com>
Date: Thu, 6 Sep 2018 20:40:39 -0700
From: Roopa Prabhu <roopa@...ulusnetworks.com>
To: Patrick Ruddy <pruddy@...tta.att-mail.com>
Cc: netdev <netdev@...r.kernel.org>,
Jiří Pírko <jiri@...nulli.us>,
Stephen Hemminger <stephen@...workplumber.org>
Subject: Re: [PATCH net-next v3 1/2] netlink: ipv4 igmp join notifications
On Thu, Sep 6, 2018 at 2:10 AM, Patrick Ruddy
<pruddy@...tta.att-mail.com> wrote:
> Some userspace applications need to know about IGMP joins from the
> kernel for 2 reasons:
> 1. To allow the programming of multicast MAC filters in hardware
> 2. To form a multicast FORUS list for non link-local multicast
> groups to be sent to the kernel and from there to the interested
> party.
> (1) can be fulfilled but simply sending the hardware multicast MAC
> address to be programmed but (2) requires the L3 address to be sent
> since this cannot be constructed from the MAC address whereas the
> reverse translation is a standard library function.
>
> This commit provides addition and deletion of multicast addresses
> using the RTM_NEWMDB and RTM_DELMDB messages with AF_INET. It also
> provides the RTM_GETMDB extension to allow multicast join state to
> be read from the kernel.
>
> Signed-off-by: Patrick Ruddy <pruddy@...tta.att-mail.com>
> ---
> v3 rework to use RTM_***MDB messages as per review comments.
Patrick, this version seems to be using RTM_***MDB msgs with the
RTM_*ADDR format.
We cant do that...because existing RTM_MDB users will be confused.
My request was to evaluate RTM_***MDB msg format. see
nlmsg_populate_mdb_fill for details.
If you can wait a day or two I can share some experimental code that
moves high level RTM_*MDB msg handling into net/core/rtnetlink.c
similar to RTM_*FDB
>
> net/ipv4/igmp.c | 139 ++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 139 insertions(+)
>
> diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
> index 4da39446da2d..aed819e2ea93 100644
> --- a/net/ipv4/igmp.c
> +++ b/net/ipv4/igmp.c
> @@ -86,6 +86,7 @@
> #include <linux/inetdevice.h>
> #include <linux/igmp.h>
> #include <linux/if_arp.h>
> +#include <net/netlink.h>
> #include <linux/rtnetlink.h>
> #include <linux/times.h>
> #include <linux/pkt_sched.h>
> @@ -1385,6 +1386,91 @@ static void ip_mc_hash_remove(struct in_device *in_dev,
> }
>
>
> +static int fill_addr(struct sk_buff *skb, struct net_device *dev, __be32 addr,
> + int type, unsigned int flags)
> +{
> + struct nlmsghdr *nlh;
> + struct ifaddrmsg *ifm;
> +
> + nlh = nlmsg_put(skb, 0, 0, type, sizeof(*ifm), flags);
> + if (!nlh)
> + return -EMSGSIZE;
> +
> + ifm = nlmsg_data(nlh);
> + ifm->ifa_family = AF_INET;
> + ifm->ifa_prefixlen = 32;
> + ifm->ifa_flags = IFA_F_PERMANENT;
> + ifm->ifa_scope = RT_SCOPE_LINK;
> + ifm->ifa_index = dev->ifindex;
> +
> + if (nla_put_in_addr(skb, IFA_ADDRESS, addr))
> + goto nla_put_failure;
> + nlmsg_end(skb, nlh);
> + return 0;
> +
> +nla_put_failure:
> + nlmsg_cancel(skb, nlh);
> + return -EMSGSIZE;
> +}
> +
> +static inline size_t addr_nlmsg_size(void)
> +{
> + return NLMSG_ALIGN(sizeof(struct ifaddrmsg))
> + + nla_total_size(sizeof(__be32));
> +}
> +
> +static void ip_mc_addr_notify(struct net_device *dev, __be32 addr, int type)
> +{
> + struct net *net = dev_net(dev);
> + struct sk_buff *skb;
> + int err = -ENOBUFS;
> +
> + skb = nlmsg_new(addr_nlmsg_size(), GFP_ATOMIC);
> + if (!skb)
> + goto errout;
> +
> + err = fill_addr(skb, dev, addr, type, 0);
> + if (err < 0) {
> + WARN_ON(err == -EMSGSIZE);
> + kfree_skb(skb);
> + goto errout;
> + }
> + rtnl_notify(skb, net, 0, RTNLGRP_MDB, NULL, GFP_ATOMIC);
> + return;
> +errout:
> + if (err < 0)
> + rtnl_set_sk_err(net, RTNLGRP_MDB, err);
> +}
> +
> +int ip_mc_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb,
> + struct net_device *dev)
> +{
> + int s_idx;
> + int idx = 0;
> + struct ip_mc_list *im;
> + struct in_device *in_dev;
> +
> + ASSERT_RTNL();
> +
> + s_idx = cb->args[2];
> + in_dev = __in_dev_get_rtnl(dev);
> +
> + for_each_pmc_rtnl(in_dev, im) {
> + if (idx < s_idx)
> + continue;
> + if (fill_addr(skb, dev, im->multiaddr, RTM_NEWMDB,
> + NLM_F_MULTI) < 0)
> + goto done;
> + nl_dump_check_consistent(cb, nlmsg_hdr(skb));
> + idx++;
> + }
> +
> + done:
> + cb->args[2] = idx;
> +
> + return skb->len;
> +}
> +
> /*
> * A socket has joined a multicast group on device dev.
> */
> @@ -1430,6 +1516,8 @@ static void __ip_mc_inc_group(struct in_device *in_dev, __be32 addr,
> igmpv3_del_delrec(in_dev, im);
> #endif
> igmp_group_added(im);
> +
> + ip_mc_addr_notify(in_dev->dev, addr, RTM_NEWMDB);
> if (!in_dev->dead)
> ip_rt_multicast_event(in_dev);
> out:
> @@ -1661,6 +1749,8 @@ void ip_mc_dec_group(struct in_device *in_dev, __be32 addr)
> in_dev->mc_count--;
> igmp_group_dropped(i);
> ip_mc_clear_src(i);
> + ip_mc_addr_notify(in_dev->dev, addr,
> + RTM_DELMDB);
>
> if (!in_dev->dead)
> ip_rt_multicast_event(in_dev);
> @@ -3051,6 +3141,53 @@ static struct notifier_block igmp_notifier = {
> .notifier_call = igmp_netdev_event,
> };
>
> +static int igmp_mc_dump_ifaddrs(struct sk_buff *skb,
> + struct netlink_callback *cb)
> +{
> + struct net *net = sock_net(skb->sk);
> + int h, s_h;
> + int idx, s_idx;
> + struct net_device *dev;
> + struct in_device *in_dev;
> + struct hlist_head *head;
> +
> + s_h = cb->args[0];
> + idx = cb->args[1];
> + s_idx = idx;
> +
> + for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {
> + idx = 0;
> + head = &net->dev_index_head[h];
> + rcu_read_lock();
> + cb->seq = atomic_read(&net->ipv4.dev_addr_genid) ^
> + net->dev_base_seq;
> + hlist_for_each_entry_rcu(dev, head, index_hlist) {
> + if (idx < s_idx)
> + goto cont;
> + if (h > s_h || idx > s_idx)
> + cb->args[2] = 0;
> + in_dev = __in_dev_get_rcu(dev);
> + if (!in_dev)
> + goto cont;
> +
> + /* loop over multicast addresses */
> + if (ip_mc_dump_ifaddr(skb, cb, dev) < 0) {
> + rcu_read_unlock();
> + goto done;
> + }
> +cont:
> + idx++;
> + }
> + rcu_read_unlock();
> + }
> +
> +done:
> + cb->args[0] = h;
> + cb->args[1] = idx;
> +
> + return skb->len;
> +}
> +
> int __init igmp_mc_init(void)
> {
> #if defined(CONFIG_PROC_FS)
> @@ -3064,6 +3201,8 @@ int __init igmp_mc_init(void)
> goto reg_notif_fail;
> return 0;
>
> + rtnl_register(PF_INET, RTM_GETMDB, NULL, igmp_mc_dump_ifaddrs, 0);
> +
> reg_notif_fail:
> unregister_pernet_subsys(&igmp_net_ops);
> return err;
> --
> 2.17.1
>
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