Switch if_nameindex(3) to use the new NET_RT_IFNAMES sysctl to get the

list of interface names. At the same time switch if_nametoindex(3) and
if_indextoname(3) to use if_nameindex(3) instead of getifaddrs(3).
if_nameindex(3) exposes much less then getifaddrs(3) and is allowed by
pledge(2).
With and OK deraadt@

3 files changed, 73 insertions, 88 deletions

diff --git a/src/lib/libc/net/if_indextoname.c b/src/lib/libc/net/if_indextoname.c
index f1c65966df..affa42551e 100644
--- a/src/lib/libc/net/if_indextoname.c
+++ b/src/lib/libc/net/if_indextoname.c
@@ -1,7 +1,8 @@
-/*      $OpenBSD: if_indextoname.c,v 1.10 2015/09/14 10:47:01 guenther Exp $    */
+/*      $OpenBSD: if_indextoname.c,v 1.11 2015/10/23 13:09:19 claudio Exp $     */
 /*      $KAME: if_indextoname.c,v 1.6 2000/11/07 22:33:25 jinmei Exp $  */
 
 /*-
+ * Copyright (c) 2015 Claudio Jeker <claudio@openbsd.org>
  * Copyright (c) 1997, 2000
  *      Berkeley Software Design, Inc.  All rights reserved.
  *
@@ -28,9 +29,7 @@
 
 #include <sys/types.h>
 #include <sys/socket.h>
-#include <net/if_dl.h>
 #include <net/if.h>
-#include <ifaddrs.h>
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
@@ -59,29 +58,21 @@
 char *
 if_indextoname(unsigned int ifindex, char *ifname)
 {
-        struct ifaddrs *ifaddrs, *ifa;
-        int error = 0;
+        struct if_nameindex *ifni, *ifni2;
 
-        if (getifaddrs(&ifaddrs) < 0)
-                return(NULL);   /* getifaddrs properly set errno */
+        if ((ifni = if_nameindex()) == NULL)
+                return NULL;
 
-        for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
-                if (ifa->ifa_addr &&
-                    ifa->ifa_addr->sa_family == AF_LINK &&
-                    ifindex == ((struct sockaddr_dl*)ifa->ifa_addr)->sdl_index)
-                        break;
+        for (ifni2 = ifni; ifni2->if_index != 0; ifni2++) {
+                if (ifni2->if_index == ifindex) {
+                        strlcpy(ifname, ifni2->if_name, IFNAMSIZ);
+                        if_freenameindex(ifni);
+                        return ifname;
+                }
         }
 
-        if (ifa == NULL) {
-                error = ENXIO;
-                ifname = NULL;
-        }
-        else
-                strlcpy(ifname, ifa->ifa_name, IFNAMSIZ);
-
-        freeifaddrs(ifaddrs);
-
-        errno = error;
-        return(ifname);
+        if_freenameindex(ifni);
+        errno = ENXIO;
+        return NULL;
 }
 DEF_WEAK(if_indextoname);
diff --git a/src/lib/libc/net/if_nameindex.c b/src/lib/libc/net/if_nameindex.c
index c5a771869b..11c544b20e 100644
--- a/src/lib/libc/net/if_nameindex.c
+++ b/src/lib/libc/net/if_nameindex.c
@@ -1,7 +1,8 @@
-/*      $OpenBSD: if_nameindex.c,v 1.10 2010/09/24 13:29:29 claudio Exp $       */
+/*      $OpenBSD: if_nameindex.c,v 1.11 2015/10/23 13:09:19 claudio Exp $       */
 /*      $KAME: if_nameindex.c,v 1.7 2000/11/24 08:17:20 itojun Exp $    */
 
 /*-
+ * Copyright (c) 2015 Claudio Jeker <claudio@openbsd.org>
  * Copyright (c) 1997, 2000
  *      Berkeley Software Design, Inc.  All rights reserved.
  *
@@ -28,11 +29,11 @@
 
 #include <sys/types.h>
 #include <sys/socket.h>
-#include <net/if_dl.h>
+#include <sys/sysctl.h>
 #include <net/if.h>
-#include <ifaddrs.h>
 #include <stdlib.h>
 #include <string.h>
+#include <errno.h>
 
 /*
  * From RFC 2553:
@@ -77,66 +78,62 @@
 struct if_nameindex *
 if_nameindex(void)
 {
-        struct ifaddrs *ifaddrs, *ifa;
-        unsigned int ni;
-        size_t nbytes;
-        struct if_nameindex *ifni, *ifni2;
+        struct if_nameindex_msg *ifnm = NULL;   
+        struct if_nameindex *ifni = NULL, *ifni2;
         char *cp;
+        size_t nbytes, needed;
+        unsigned int ni, i;
+        int mib[6];
 
-        if (getifaddrs(&ifaddrs) < 0)
-                return(NULL);
+        mib[0] = CTL_NET;
+        mib[1] = PF_ROUTE;
+        mib[2] = 0;             /* protocol */
+        mib[3] = 0;             /* not used */
+        mib[4] = NET_RT_IFNAMES;
+        mib[5] = 0;             /* no flags */
+        while (1) {
+                struct if_nameindex_msg *buf = NULL;    
 
-        /*
-         * First, find out how many interfaces there are, and how
-         * much space we need for the string names.
-         */
-        ni = 0;
-        nbytes = 0;
-        for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
-                if (ifa->ifa_addr &&
-                    ifa->ifa_addr->sa_family == AF_LINK) {
-                        nbytes += strlen(ifa->ifa_name) + 1;
-                        ni++;
+                if (sysctl(mib, 6, NULL, &needed, NULL, 0) == -1)
+                        goto out;
+                if (needed == 0)
+                        break;
+                if ((buf = realloc(ifnm, needed)) == NULL)
+                        goto out;
+                ifnm = buf;
+                if (sysctl(mib, 6, ifnm, &needed, NULL, 0) == -1) {
+                        if (errno == ENOMEM)
+                                continue;
+                        goto out;
                 }
+                break;
         }
 
         /*
-         * Next, allocate a chunk of memory, use the first part
-         * for the array of structures, and the last part for
-         * the strings.
+         * Allocate a chunk of memory, use the first part for the array of
+         * structures, and the last part for the strings.
          */
-        cp = malloc((ni + 1) * sizeof(struct if_nameindex) + nbytes);
-        ifni = (struct if_nameindex *)cp;
+        ni = needed / sizeof(*ifnm);
+        ifni = calloc(ni + 1, sizeof(struct if_nameindex) + IF_NAMESIZE);
         if (ifni == NULL)
                 goto out;
-        cp += (ni + 1) * sizeof(struct if_nameindex);
+        cp = (char *)(ifni + (ni + 1));
 
-        /*
-         * Now just loop through the list of interfaces again,
-         * filling in the if_nameindex array and making copies
-         * of all the strings.
-         */
         ifni2 = ifni;
-        for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
-                if (ifa->ifa_addr &&
-                    ifa->ifa_addr->sa_family == AF_LINK) {
-                        ifni2->if_index =
-                            ((struct sockaddr_dl*)ifa->ifa_addr)->sdl_index;
-                        ifni2->if_name = cp;
-                        nbytes = strlen(ifa->ifa_name) + 1;
-                        memcpy(cp, ifa->ifa_name, nbytes);
-                        ifni2++;
-                        cp += nbytes;
-                }
+        for (i = 0; i < ni; i++) {
+                ifni2->if_index = ifnm[i].if_index;
+                /* don't care about truncation */
+                strlcpy(cp, ifnm[i].if_name, IF_NAMESIZE);
+                ifni2->if_name = cp;
+                ifni2++;
+                cp += IF_NAMESIZE;
         }
-        /*
-         * Finally, don't forget to terminate the array.
-         */
+        /* Finally, terminate the array. */
         ifni2->if_index = 0;
         ifni2->if_name = NULL;
 out:
-        freeifaddrs(ifaddrs);
-        return(ifni);
+        free(ifnm);
+        return ifni;
 }
 
 void
@@ -144,3 +141,5 @@ if_freenameindex(struct if_nameindex *ptr)
 {
         free(ptr);
 }
+DEF_WEAK(if_nameindex);
+DEF_WEAK(if_freenameindex);
diff --git a/src/lib/libc/net/if_nametoindex.c b/src/lib/libc/net/if_nametoindex.c
index 8b2cbf743f..7a4492e37d 100644
--- a/src/lib/libc/net/if_nametoindex.c
+++ b/src/lib/libc/net/if_nametoindex.c
@@ -1,7 +1,8 @@
-/*      $OpenBSD: if_nametoindex.c,v 1.9 2015/09/14 10:47:01 guenther Exp $     */
+/*      $OpenBSD: if_nametoindex.c,v 1.10 2015/10/23 13:09:19 claudio Exp $     */
 /*      $KAME: if_nametoindex.c,v 1.5 2000/11/24 08:04:40 itojun Exp $  */
 
 /*-
+ * Copyright (c) 2015 Claudio Jeker <claudio@openbsd.org>
  * Copyright (c) 1997, 2000
  *      Berkeley Software Design, Inc.  All rights reserved.
  *
@@ -29,8 +30,6 @@
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <net/if.h>
-#include <net/if_dl.h>
-#include <ifaddrs.h>
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
@@ -57,26 +56,22 @@
 unsigned int
 if_nametoindex(const char *ifname)
 {
-        struct ifaddrs *ifaddrs, *ifa;
-        unsigned int ni;
+        struct if_nameindex *ifni, *ifni2;
+        unsigned int index;
 
-        if (getifaddrs(&ifaddrs) < 0)
+        if ((ifni = if_nameindex()) == NULL)
                 return(0);
 
-        ni = 0;
-
-        for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
-                if (ifa->ifa_addr &&
-                    ifa->ifa_addr->sa_family == AF_LINK &&
-                    strcmp(ifa->ifa_name, ifname) == 0) {
-                        ni = ((struct sockaddr_dl*)ifa->ifa_addr)->sdl_index;
-                        break;
+        for (ifni2 = ifni; ifni2->if_index != 0; ifni2++) {
+                if (strcmp(ifni2->if_name, ifname) == 0) {
+                        index = ifni2->if_index;
+                        if_freenameindex(ifni);
+                        return index;
                 }
         }
 
-        freeifaddrs(ifaddrs);
-        if (!ni)
-                errno = ENXIO;
-        return(ni);
+        if_freenameindex(ifni);
+        errno = ENXIO;
+        return 0;
 }
 DEF_WEAK(if_nametoindex);