nexthop: Add ability to specify group type

Next patches are going to add a 'resilient' nexthop group type, so allow
users to specify the type using the 'type' argument. Currently, only
'mpath' type is supported.

These two commands are equivalent:

 # ip nexthop add id 10 group 1/2/3
 # ip nexthop add id 10 group 1/2/3 type mpath

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: David Ahern <dsahern@kernel.org>

ip/ipnexthop.c

@@ -42,8 +42,10 @@ static void usage(void)
 		"SELECTOR := [ id ID ] [ dev DEV ] [ vrf NAME ] [ master DEV ]\n"
 		"            [ groups ] [ fdb ]\n"
 		"NH := { blackhole | [ via ADDRESS ] [ dev DEV ] [ onlink ]\n"
-		"        [ encap ENCAPTYPE ENCAPHDR ] | group GROUP [ fdb ] }\n"
+		"        [ encap ENCAPTYPE ENCAPHDR ] |\n"
+		"        group GROUP [ fdb ] [ type TYPE ] }\n"
 		"GROUP := [ <id[,weight]>/<id[,weight]>/... ]\n"
+		"TYPE := { mpath }\n"
 		"ENCAPTYPE := [ mpls ]\n"
 		"ENCAPHDR := [ MPLSLABEL ]\n");
 	exit(-1);
@@ -327,6 +329,32 @@ static int add_nh_group_attr(struct nlmsghdr *n, int maxlen, char *argv)
 	return addattr_l(n, maxlen, NHA_GROUP, grps, count * sizeof(*grps));
 }
 
+static int read_nh_group_type(const char *name)
+{
+	if (strcmp(name, "mpath") == 0)
+		return NEXTHOP_GRP_TYPE_MPATH;
+
+	return __NEXTHOP_GRP_TYPE_MAX;
+}
+
+static void parse_nh_group_type(struct nlmsghdr *n, int maxlen, int *argcp,
+				char ***argvp)
+{
+	char **argv = *argvp;
+	int argc = *argcp;
+	__u16 type;
+
+	NEXT_ARG();
+	type = read_nh_group_type(*argv);
+	if (type > NEXTHOP_GRP_TYPE_MAX)
+		invarg("\"type\" value is invalid\n", *argv);
+
+	*argcp = argc;
+	*argvp = argv;
+
+	addattr16(n, maxlen, NHA_GROUP_TYPE, type);
+}
+
 static int ipnh_parse_id(const char *argv)
 {
 	__u32 id;
@@ -409,6 +437,8 @@ static int ipnh_modify(int cmd, unsigned int flags, int argc, char **argv)
 
 			if (add_nh_group_attr(&req.n, sizeof(req), *argv))
 				invarg("\"group\" value is invalid\n", *argv);
+		} else if (!strcmp(*argv, "type")) {
+			parse_nh_group_type(&req.n, sizeof(req), &argc, &argv);
 		} else if (matches(*argv, "protocol") == 0) {
 			__u32 prot;
 

man/man8/ip-nexthop.8

@@ -54,7 +54,9 @@ ip-nexthop \- nexthop object management
 .BR fdb " ] | "
 .B  group
 .IR GROUP " [ "
-.BR fdb " ] } "
+.BR fdb " ] [ "
+.B type
+.IR TYPE " ] } "
 
 .ti -8
 .IR ENCAP " := [ "
@@ -71,6 +73,10 @@ ip-nexthop \- nexthop object management
 .IR GROUP " := "
 .BR id "[," weight "[/...]"
 
+.ti -8
+.IR TYPE " := { "
+.BR mpath " }"
+
 .SH DESCRIPTION
 .B ip nexthop
 is used to manipulate entries in the kernel's nexthop tables.
@@ -122,9 +128,18 @@ is a set of encapsulation attributes specific to the
 .in -2
 
 .TP
-.BI group " GROUP"
+.BI group " GROUP [ " type " TYPE ]"
 create a nexthop group. Group specification is id with an optional
 weight (id,weight) and a '/' as a separator between entries.
+.sp
+.I TYPE
+is a string specifying the nexthop group type. Namely:
+
+.in +8
+.BI mpath
+- Multipath nexthop group backed by the hash-threshold algorithm. The
+default when the type is unspecified.
+
 .TP
 .B blackhole
 create a blackhole nexthop