net: ip6mr: add RTM_GETROUTE netlink op

jira LE-2522
Rebuild_History Non-Buildable kernel-5.14.0-503.29.1.el9_5
commit-author David Lamparter <[email protected]>
commit d7c31cb
Empty-Commit: Cherry-Pick Conflicts during history rebuild.
Will be included in final tarball splat. Ref for failed cherry-pick at:
ciq/ciq_backports/kernel-5.14.0-503.29.1.el9_5/d7c31cbd.failed

The IPv6 multicast routing code previously implemented only the dump
variant of RTM_GETROUTE.  Implement single MFC item retrieval by copying
and adapting the respective IPv4 code.

Tested against FRRouting's IPv6 PIM stack.

	Signed-off-by: David Lamparter <[email protected]>
	Reviewed-by: Nikolay Aleksandrov <[email protected]>
	Reviewed-by: David Ahern <[email protected]>
	Cc: Jakub Kicinski <[email protected]>
	Signed-off-by: David S. Miller <[email protected]>
(cherry picked from commit d7c31cb)
	Signed-off-by: Jonathan Maple <[email protected]>

# Conflicts:
#	net/ipv6/ip6mr.c

Author: PlaidCat

ciq/ciq_backports/kernel-5.14.0-503.29.1.el9_5/d7c31cbd.failed

@@ -0,0 +1,45 @@
+net: ip6mr: add RTM_GETROUTE netlink op
+
+jira LE-2522
+Rebuild_History Non-Buildable kernel-5.14.0-503.29.1.el9_5
+commit-author David Lamparter <[email protected]>
+commit d7c31cbde4bc6756d1a11747d2b99bc627001c86
+Empty-Commit: Cherry-Pick Conflicts during history rebuild.
+Will be included in final tarball splat. Ref for failed cherry-pick at:
+ciq/ciq_backports/kernel-5.14.0-503.29.1.el9_5/d7c31cbd.failed
+
+The IPv6 multicast routing code previously implemented only the dump
+variant of RTM_GETROUTE.  Implement single MFC item retrieval by copying
+and adapting the respective IPv4 code.
+
+Tested against FRRouting's IPv6 PIM stack.
+
+	Signed-off-by: David Lamparter <[email protected]>
+	Reviewed-by: Nikolay Aleksandrov <[email protected]>
+	Reviewed-by: David Ahern <[email protected]>
+	Cc: Jakub Kicinski <[email protected]>
+	Signed-off-by: David S. Miller <[email protected]>
+(cherry picked from commit d7c31cbde4bc6756d1a11747d2b99bc627001c86)
+	Signed-off-by: Jonathan Maple <[email protected]>
+
+# Conflicts:
+#	net/ipv6/ip6mr.c
+diff --cc net/ipv6/ip6mr.c
+index 82ffa9515d31,d546fc09d803..000000000000
+--- a/net/ipv6/ip6mr.c
++++ b/net/ipv6/ip6mr.c
+@@@ -89,7 -94,9 +89,13 @@@ static int ip6mr_cache_report(struct mr
+  			      mifi_t mifi, int assert);
+  static void mr6_netlink_event(struct mr_table *mrt, struct mfc6_cache *mfc,
+  			      int cmd);
+++<<<<<<< HEAD
+ +static void mrt6msg_netlink_event(struct mr_table *mrt, struct sk_buff *pkt);
+++=======
++ static void mrt6msg_netlink_event(const struct mr_table *mrt, struct sk_buff *pkt);
++ static int ip6mr_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
++ 			      struct netlink_ext_ack *extack);
+++>>>>>>> d7c31cbde4bc (net: ip6mr: add RTM_GETROUTE netlink op)
+  static int ip6mr_rtm_dumproute(struct sk_buff *skb,
+  			       struct netlink_callback *cb);
+  static void mroute_clean_tables(struct mr_table *mrt, int flags);
+* Unmerged path net/ipv6/ip6mr.c