[PATCH 2/3] Handle family-based parsing of IFLA_AF_SPEC attribute

[David Ahern]

The encoding of the IFLA_AF_SPEC attribute varies depending on the family
used for the request (RTM_GETLINK) message. For AF_UNSPEC the encoding
has another level of nesting for each address family with the type encoded
first. i.e.,
    af_spec = nla_nest_start(skb, IFLA_AF_SPEC)
    for each family:
        af = nla_nest_start(skb, af_ops->family)
        af_ops->fill_link_af(skb, dev, ext_filter_mask)
        nest_end
    nest_end

This allows the parser to find the address family by looking at the first
type.

Whereas AF_BRIDGE encoding is just:
    af_spec = nla_nest_start(skb, IFLA_AF_SPEC)
    br_fill_ifvlaninfo{_compressed}(skb, vg)
    nest_end

which means the parser can not use the attribute itself to know the family
to which the attribute belongs.

Signed-off-by: David Ahern <dsa at cumulusnetworks.com>
---
 lib/route/link.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 68 insertions(+), 13 deletions(-)

diff --git a/lib/route/link.c b/lib/route/link.c
index 3cb62df95d6a..b8e333c31a3a 100644
--- a/lib/route/link.c
+++ b/lib/route/link.c
@@ -489,6 +489,56 @@ int rtnl_link_info_parse(struct rtnl_link *link, struct nlattr **tb)
 	return 0;
 }
 
+static int parse_af_spec_unspec(struct rtnl_link *link, struct nlattr *attr)
+{
+	struct nlattr *af_attr;
+	int remaining;
+	int err = 0;
+
+	nla_for_each_nested(af_attr, attr, remaining) {
+		struct rtnl_link_af_ops *af_ops;
+
+		af_ops = af_lookup_and_alloc(link, nla_type(af_attr));
+		if (af_ops && af_ops->ao_parse_af) {
+			char *af_data = link->l_af_data[nla_type(af_attr)];
+
+			err = af_ops->ao_parse_af(link, af_attr, af_data);
+			if (err < 0) {
+				goto errout;
+			}
+		}
+
+	}
+
+	link->ce_mask |= LINK_ATTR_AF_SPEC;
+errout:
+	return err;
+}
+
+static int parse_af_spec_bridge(struct rtnl_link *link, struct nlattr *attr)
+{
+	struct rtnl_link_af_ops *af_ops;
+	struct nlattr *af_attr;
+	char *af_data;
+	int remaining;
+	int err = 0;
+
+	af_ops = af_lookup_and_alloc(link, AF_BRIDGE);
+	af_data = link->l_af_data[AF_BRIDGE];
+
+	if (af_ops && af_ops->ao_parse_af) {
+		nla_for_each_nested(af_attr, attr, remaining) {
+			err = af_ops->ao_parse_af(link, af_attr, af_data);
+			if (err < 0)
+				goto errout;
+		}
+	}
+
+	link->ce_mask |= LINK_ATTR_AF_SPEC;
+errout:
+	return err;
+}
+
 static int link_msg_parser(struct nl_cache_ops *ops, struct sockaddr_nl *who,
 			   struct nlmsghdr *n, struct nl_parser_param *pp)
 {
@@ -601,21 +651,26 @@ static int link_msg_parser(struct nl_cache_ops *ops, struct sockaddr_nl *who,
 	}
 
 	if (tb[IFLA_AF_SPEC]) {
-		struct nlattr *af_attr;
-		int remaining;
-
-		nla_for_each_nested(af_attr, tb[IFLA_AF_SPEC], remaining) {
-			af_ops = af_lookup_and_alloc(link, nla_type(af_attr));
-			if (af_ops && af_ops->ao_parse_af) {
-				char *af_data = link->l_af_data[nla_type(af_attr)];
-
-				err = af_ops->ao_parse_af(link, af_attr, af_data);
-				if (err < 0)
-					goto errout;
-			}
+		struct nl_cache *cache = (struct nl_cache *) pp->pp_arg;
 
+		/* parsing of IFLA_AF_SPEC is dependent on the family used
+		 * in the request message which is conveniently passed via
+		 * the nl_parser_param arg.
+		 */
+		switch(cache->c_iarg1) {
+		case AF_BRIDGE:
+			err = parse_af_spec_bridge(link, tb[IFLA_AF_SPEC]);
+			break;
+		case AF_UNSPEC:
+			err = parse_af_spec_unspec(link, tb[IFLA_AF_SPEC]);
+			break;
+		default:
+			err = -EINVAL;
+			NL_DBG(1, "IFLA_AF_SPEC parsing not implemented for family %d\n",
+				family);
 		}
-		link->ce_mask |= LINK_ATTR_AF_SPEC;
+		if (err)
+			goto errout;
 	}
 
 	if (tb[IFLA_PROMISCUITY]) {
-- 
2.1.4