[PATCH] Change rtnl_link_af_ops.ao_override_rtm behavior

[jef.oliver at intel.com]

From: Jef Oliver <jef.oliver at intel.com>

rtnl_link_af_ops.ao_override_rtm allows for a link module to
override the change request type being sent to the kernel. More
specifically, the default change request type is RTM_NEWLINK.
Some link change requests require the reqeust type to be set to
RTM_SETLINK. This is the case for IFLA_PROTINFO specific
attributes for a link that is slave to a bridge.

Currently, ao_override_rtm is static to the address family type.
So, all changes submitted to AF_BRIDGE override the link change
request type. The override only needs to happen if IFLA_PROTINFO
attributes are appended to the link change request.

This patch changes ao_override_rtm from a const integer to a
function pointer that allows for a link module to determine if
the override needs to actually happen.

Currently, only the bridge module uses this functionality. If
bridge flags are applied to a link (bdpu blocking, learning,
fast leave, etc...), these flags are nested in IFLA_PROTINFO. If
the flags are present, the link change request type will be
overridden as RTM_SETLINK.

This fixes the ability to set a bridge link up or down by using
the correct RTM_NEWLINK link change request type.

$ sudo src/nl-link-set -n br2 --state=down
Changed bridge br2 ether a6:e6:94:8c:61:ec
    <broadcast,multicast,up,running,lowerup> group 0

$ ip link show
br2: <BROADCAST,MULTICAST> mtu 1500 qdisc noqueue
    state DOWN mode DEFAULT group default qlen 1000

$ sudo src/nl-link-set -n br2 --state=up
Changed bridge br2 ether a6:e6:94:8c:61:ec
    <broadcast,multicast> group 0

$ ip link show
br2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue
    state UNKNOWN mode DEFAULT group default qlen 1000

Signed-off-by: Jef Oliver <jef.oliver at intel.com>
---
 include/netlink-private/route/link/api.h |  6 +++---
 lib/route/link.c                         |  6 +++---
 lib/route/link/bridge.c                  | 16 +++++++++++++++-
 3 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/include/netlink-private/route/link/api.h b/include/netlink-private/route/link/api.h
index 47fed6f..6d30bf7 100644
--- a/include/netlink-private/route/link/api.h
+++ b/include/netlink-private/route/link/api.h
@@ -149,11 +149,11 @@ struct rtnl_link_af_ops
 
 	/* RTM_NEWLINK override
 	 *
-	 * Called if a change link request is set to the kernel. If this is set
-	 * to anything other than zero, RTM_NEWLINK will be overriden with
+	 * Called if a change link request is set to the kernel. If this returns
+	 * anything other than zero, RTM_NEWLINK will be overriden with
 	 * RTM_SETLINK when rtnl_link_build_change_request() is called.
 	 */
-	const int ao_override_rtm;
+	int		      (*ao_override_rtm)(struct rtnl_link *);
 
 	/** Called if a link message is sent to the kernel. Must append the
 	 * link protocol specific attributes to the message. (IFLA_PROTINFO) */
diff --git a/lib/route/link.c b/lib/route/link.c
index 4384ea1..de3c393 100644
--- a/lib/route/link.c
+++ b/lib/route/link.c
@@ -116,12 +116,12 @@ static int af_free(struct rtnl_link *link, struct rtnl_link_af_ops *ops,
 	return 0;
 }
 
-static int af_request_type(int af_type)
+static int af_request_type(int af_type, struct rtnl_link *changes)
 {
 	struct rtnl_link_af_ops *ops;
 
 	ops = rtnl_link_af_ops_lookup(af_type);
-	if (ops && ops->ao_override_rtm)
+	if (ops && ops->ao_override_rtm(changes))
 		return RTM_SETLINK;
 
 	return RTM_NEWLINK;
@@ -1732,7 +1732,7 @@ int rtnl_link_build_change_request(struct rtnl_link *orig,
 	    !strcmp(orig->l_name, changes->l_name))
 		changes->ce_mask &= ~LINK_ATTR_IFNAME;
 
-	rt = af_request_type(orig->l_family);
+	rt = af_request_type(orig->l_family, changes);
 
 	if ((err = build_link_msg(rt, &ifi, changes, flags, result)) < 0)
 		goto errout;
diff --git a/lib/route/link/bridge.c b/lib/route/link/bridge.c
index b9d05bc..2d95faf 100644
--- a/lib/route/link/bridge.c
+++ b/lib/route/link/bridge.c
@@ -307,6 +307,20 @@ nla_put_failure:
 	return -NLE_MSGSIZE;
 }
 
+static int bridge_override_rtm(struct rtnl_link *link) {
+        struct bridge_data *bd;
+
+        if (!rtnl_link_is_bridge(link))
+                return 0;
+
+        bd = bridge_data(link);
+
+        if (bd->ce_mask & BRIDGE_ATTR_FLAGS)
+                return 1;
+
+        return 0;
+}
+
 static int bridge_get_af(struct nl_msg *msg, uint32_t *ext_filter_mask)
 {
 	*ext_filter_mask |= RTEXT_FILTER_BRVLAN;
@@ -961,7 +975,7 @@ static struct rtnl_link_af_ops bridge_ops = {
 	.ao_fill_af			= &bridge_fill_af,
 	.ao_fill_pi			= &bridge_fill_pi,
 	.ao_fill_pi_flags	= NLA_F_NESTED,
-	.ao_override_rtm	= 1,
+	.ao_override_rtm		= &bridge_override_rtm,
 	.ao_fill_af_no_nest	= 1,
 };
 
-- 
2.15.0