[PATCH iproute2-next 3/3] Improve batch times by caching link lookups

[David Ahern <dsahern@kernel.org>]

From: David Ahern <dsahern@gmail.com>

ip route (for example) uses ll_name_to_index to convert the user given
device name to an index. At the moment ll_name_to_index uses if_nametoindex
which is ioctl based and does not cache the result. When using a batch file
this means the same device lookups can be done repeatedly adding unnecessary
overhead (socket + ioctl + close for each device lookup).

Add a new function, ll_link_get, to send a netlink based RTM_GETLINK. If
successful, cache the result in idx_head and name_head so future lookups
can re-use the entry. Update ll_name_to_index to use ll_link_get over
if_nametoindex.

With this change the time to install 720,022 routes with 2 ecmp nexthops
where the nexthop device is given is reduced from 30.7 seconds to 17.6
seconds.

Signed-off-by: David Ahern <dsahern@gmail.com>
---
 lib/ll_map.c | 44 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/lib/ll_map.c b/lib/ll_map.c
index 8e8a0b1e9c9d..46c78df08c11 100644
--- a/lib/ll_map.c
+++ b/lib/ll_map.c
@@ -192,6 +192,46 @@ int ll_index_to_flags(unsigned idx)
 	return im ? im->flags : -1;
 }
 
+static int ll_link_get(const char *name)
+{
+	struct {
+		struct nlmsghdr		n;
+		struct ifinfomsg	ifm;
+		char			buf[1024];
+	} req = {
+		.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
+		.n.nlmsg_flags = NLM_F_REQUEST,
+		.n.nlmsg_type = RTM_GETLINK,
+	};
+	__u32 filt_mask = RTEXT_FILTER_VF | RTEXT_FILTER_SKIP_STATS;
+	struct rtnl_handle rth = {};
+	struct nlmsghdr *answer;
+	int rc = 0;
+
+	if (rtnl_open(&rth, 0) < 0)
+		return 0;
+
+	addattr32(&req.n, sizeof(req), IFLA_EXT_MASK, filt_mask);
+	addattr_l(&req.n, sizeof(req), IFLA_IFNAME, name,
+		  strlen(name) + 1);
+
+	if (rtnl_talk(&rth, &req.n, &answer) < 0)
+		goto out;
+
+	/* add entry to cache */
+	rc  = ll_remember_index(answer, NULL);
+	if (!rc) {
+		struct ifinfomsg *ifm = NLMSG_DATA(answer);
+
+		rc = ifm->ifi_index;
+	}
+
+	free(answer);
+out:
+	rtnl_close(&rth);
+	return rc;
+}
+
 unsigned ll_name_to_index(const char *name)
 {
 	const struct ll_cache *im;
@@ -204,7 +244,9 @@ unsigned ll_name_to_index(const char *name)
 	if (im)
 		return im->index;
 
-	idx = if_nametoindex(name);
+	idx = ll_link_get(name);
+	if (idx == 0)
+		idx = if_nametoindex(name);
 	if (idx == 0)
 		idx = ll_idx_a2n(name);
 	return idx;
-- 
2.11.0