Re: [PATCH net-next 1/1] net: Add new protocol attribute to IP addresses

This patch adds a new protocol attribute to IPv4 and IPv6 addresses.
Inspiration was taken from the protocol attribute of routes. User space
applications like iproute2 can set/get the protocol with the Netlink API.

The attribute is stored as an 8-bit unsigned int. Only IFAPROT_UNSPEC is
defined. The rest of the available ids are available for user space to
define.

Grouping addresses on their origin is useful in scenarios where you want
to distinguish between addresses coming from a specific protocol like DHCP
and addresses that have been statically set.

Tagging addresses with a string label is an existing feature that could be
used as a solution. Unfortunately the max length of a label is
15 characters, and for compatibility reasons the label must be prefixed
with the name of the device followed by a colon. Since device names also
have a max length of 15 characters, only -1 characters is guaranteed to be
available for any origin tag, which is not that much.

A reference implementation of user space setting and getting protocols
is available for iproute2:

Link: https://github.com/westermo/iproute2/commit/9a6ea18bd79f47f293e5edc7780f315ea42ff540

Signed-off-by: Jacques de Laval <redacted>
---
 include/linux/inetdevice.h   |  1 +
 include/net/addrconf.h       |  1 +
 include/net/if_inet6.h       |  2 ++
 include/uapi/linux/if_addr.h |  4 ++++
 net/ipv4/devinet.c           |  8 ++++++++
 net/ipv6/addrconf.c          | 12 ++++++++++++
 6 files changed, 28 insertions(+)

diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
index a038feb63f23..caa6b7a5b5ac 100644
--- a/include/linux/inetdevice.h
+++ b/include/linux/inetdevice.h

@@ -148,6 +148,7 @@ struct in_ifaddr {
 	unsigned char		ifa_prefixlen;
 	__u32			ifa_flags;
 	char			ifa_label[IFNAMSIZ];
+	unsigned char		ifa_proto;

 
 	/* In seconds, relative to tstamp. Expiry is at tstamp + HZ * lft. */
 	__u32			ifa_valid_lft;

diff --git a/include/net/addrconf.h b/include/net/addrconf.h
index 78ea3e332688..e53d8f4f4166 100644
--- a/include/net/addrconf.h
+++ b/include/net/addrconf.h

@@ -69,6 +69,7 @@ struct ifa6_config {
 	u32			preferred_lft;
 	u32			valid_lft;
 	u16			scope;
+	u8			ifa_proto;
 };
 
 int addrconf_init(void);

diff --git a/include/net/if_inet6.h b/include/net/if_inet6.h
index 653e7d0f65cb..f7c270b24167 100644
--- a/include/net/if_inet6.h
+++ b/include/net/if_inet6.h

@@ -73,6 +73,8 @@ struct inet6_ifaddr {
 
 	struct rcu_head		rcu;
 	struct in6_addr		peer_addr;
+
+	__u8			ifa_proto;

 };
 
 struct ip6_sf_socklist {

diff --git a/include/uapi/linux/if_addr.h b/include/uapi/linux/if_addr.h
index dfcf3ce0097f..2aa46b9c9961 100644
--- a/include/uapi/linux/if_addr.h
+++ b/include/uapi/linux/if_addr.h

@@ -35,6 +35,7 @@ enum {
 	IFA_FLAGS,
 	IFA_RT_PRIORITY,  /* u32, priority/metric for prefix route */
 	IFA_TARGET_NETNSID,
+	IFA_PROTO,
 	__IFA_MAX,
 };
 

@@ -69,4 +70,7 @@ struct ifa_cacheinfo {
 #define IFA_PAYLOAD(n) NLMSG_PAYLOAD(n,sizeof(struct ifaddrmsg))
 #endif
 
+/* ifa_protocol */
+#define IFAPROT_UNSPEC	0