From e78c7a0a9a0ef648fcbe3b35f6678a818ba4b44d Mon Sep 17 00:00:00 2001
From: Max Laier <mlaier@FreeBSD.org>
Date: Fri, 11 Jun 2010 19:35:05 +0000
Subject: [PATCH] Cache the last result from if_indextoname for printing.  This
 speeds up "arp -an" when using a lot of aliases (on a single interface).

A better fix would include a better interface for if_indextoname than
getting the whole address list from the kernel just to find the one
index->name mapping.

Reported & analyzed by:	Nick Rogers
MFC after:		3 days
---
 usr.sbin/arp/arp.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/usr.sbin/arp/arp.c b/usr.sbin/arp/arp.c
index a0e228ce3656..2ee9d67e6827 100644
--- a/usr.sbin/arp/arp.c
+++ b/usr.sbin/arp/arp.c
@@ -555,6 +555,9 @@ search(u_long addr, action_fn *action)
 /*
  * Display an arp entry
  */
+static char lifname[IF_NAMESIZE];
+static int64_t lifindex = -1;
+
 static void
 print_entry(struct sockaddr_dl *sdl,
 	struct sockaddr_inarp *addr, struct rt_msghdr *rtm)
@@ -562,7 +565,6 @@ print_entry(struct sockaddr_dl *sdl,
 	const char *host;
 	struct hostent *hp;
 	struct iso88025_sockaddr_dl_data *trld;
-	char ifname[IF_NAMESIZE];
 	int seg;
 
 	if (nflag == 0)
@@ -591,8 +593,12 @@ print_entry(struct sockaddr_dl *sdl,
 		}
 	} else
 		printf("(incomplete)");
-	if (if_indextoname(sdl->sdl_index, ifname) != NULL)
-		printf(" on %s", ifname);
+	if (sdl->sdl_index != lifindex &&
+	    if_indextoname(sdl->sdl_index, lifname) != NULL) {
+        	lifindex = sdl->sdl_index;
+		printf(" on %s", lifname);
+        } else if (sdl->sdl_index == lifindex)
+		printf(" on %s", lifname);
 	if (rtm->rtm_rmx.rmx_expire == 0)
 		printf(" permanent");
 	else {