netdev - Re: [PATCH] Netlink messages for multicast HW addr programming

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Date:	Thu, 21 Jan 2016 21:04:19 +0100
From:	Jiri Pirko <jiri@...nulli.us>
To:	Patrick Ruddy <pruddy@...cade.com>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] Netlink messages for multicast HW addr programming

Thu, Jan 21, 2016 at 12:47:54PM CET, pruddy@...cade.com wrote:
>Add RTM_NEWADDR and RTM_DELADDR netlink messages to indicate
>interest in specific multicast hardware addresses. These messages
>are sent when addressed are added or deleted from the appropriate
>interface driver.
>
>Signed-off-by: Patrick Ruddy <pruddy@...cade.com>
>
>diff --git a/net/core/dev_addr_lists.c b/net/core/dev_addr_lists.c
>index c0548d2..a0ebadd 100644
>--- a/net/core/dev_addr_lists.c
>+++ b/net/core/dev_addr_lists.c
>@@ -12,6 +12,7 @@
>  */
> 
> #include <linux/netdevice.h>
>+#include <net/netlink.h>
> #include <linux/rtnetlink.h>
> #include <linux/export.h>
> #include <linux/list.h>
>@@ -661,6 +662,62 @@ out:
> }
> EXPORT_SYMBOL(dev_mc_add_excl);
> 
>+static int fill_addr(struct sk_buff *skb, struct net_device *dev,
>+		     const unsigned char *addr, int type)
>+{
>+	struct nlmsghdr *nlh;
>+	struct ifaddrmsg *ifm;
>+
>+	nlh = nlmsg_put(skb, 0, 0, type, sizeof(*ifm), 0);
>+	if (nlh == NULL)
>+		return -EMSGSIZE;
>+
>+	ifm = nlmsg_data(nlh);
>+	ifm->ifa_family = AF_UNSPEC;
>+	ifm->ifa_prefixlen = 0;
>+	ifm->ifa_flags = IFA_F_PERMANENT;
>+	ifm->ifa_scope = RT_SCOPE_LINK;
>+	ifm->ifa_index = dev->ifindex;
>+	if (nla_put(skb, IFA_ADDRESS, dev->addr_len, addr))
>+		goto nla_put_failure;
>+	nlmsg_end(skb, nlh);

How can userspace tell if this is a multicast addr? Also, why not add
notifications for unicast addrs so we handle both the same?