Improve batch and dump times by caching link lookups

ip route uses ll_name_to_index and ll_index_to_name to convert between
device names and indices. At the moment both use for the ioctl based glibc
functions if_nametoindex and if_indextoname and does not cache the result.
When using a batch file or dumping large number of routes 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 and ll_index_to_name to use
ll_link_get and only fallback to the glibc functions if it fails.

With this change the time to install 720,022 routes with 2 ecmp nexthops
where the nexthop device is given is reduced from 31.4 seconds to 19.2
seconds. A dump of those routes drops from 13.3 to 2.8 seconds.

Signed-off-by: David Ahern <dsahern@gmail.com>

diff --git a/lib/ll_map.c b/lib/ll_map.c
index 8e8a0b1e9c9d9880bcbecccffd225fe4ebe9a1c6..2d7b65dcb8f7e3a21b726199eee4cc3719669524 100644 (file)
--- a/lib/ll_map.c
+++ b/lib/ll_map.c
@@ -152,6 +152,48 @@ static unsigned int ll_idx_a2n(const char *name)
        return idx;
 }
 
+static int ll_link_get(const char *name, int index)
+{
+       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,
+               .ifm.ifi_index = index,
+       };
+       __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);
+       if (name)
+               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;
+}
+
 const char *ll_index_to_name(unsigned int idx)
 {
        static char buf[IFNAMSIZ];
@@ -164,6 +206,12 @@ const char *ll_index_to_name(unsigned int idx)
        if (im)
                return im->name;
 
+       if (ll_link_get(NULL, idx) == idx) {
+               im = ll_get_by_index(idx);
+               if (im)
+                       return im->name;
+       }
+
        if (if_indextoname(idx, buf) == NULL)
                snprintf(buf, IFNAMSIZ, "if%u", idx);
 
@@ -204,7 +252,9 @@ unsigned ll_name_to_index(const char *name)
        if (im)
                return im->index;
 
-       idx = if_nametoindex(name);
+       idx = ll_link_get(name, 0);
+       if (idx == 0)
+               idx = if_nametoindex(name);
        if (idx == 0)
                idx = ll_idx_a2n(name);
        return idx;