Properly set error message in lookupdev() functions.

Also changes to print it better to the user.

6 files changed, 116 insertions, 29 deletions

diff --git a/src/arping.c b/src/arping.c
index d230261..98f10a9 100644
--- a/src/arping.c
+++ b/src/arping.c
@@ -110,6 +110,8 @@
 
 /**
  * OS-specific interface finding using routing table. See findif_*.c
+ * ebuf must be called with a size of at least
+ * max(LIBNET_ERRBUF_SIZE, PCAP_ERRBUF_SIZE).
  */
 const char *
 arping_lookupdev(uint32_t srcip, uint32_t dstip, char *ebuf);
@@ -1348,11 +1350,15 @@ int main(int argc, char **argv)
                 if (!dont_use_arping_lookupdev) {
                         ifname = arping_lookupdev(srcip, dstip, ebuf);
                         strip_newline(ebuf);
+                        if (!ifname) {
+                                fprintf(stderr, "arping: lookup dev: %s\n",
+                                        ebuf);
+                        }
                 }
                 if (!ifname) {
                         ifname = arping_lookupdev_default(srcip, dstip, ebuf);
                         strip_newline(ebuf);
-                        if (!dont_use_arping_lookupdev) {
+                        if (ifname && !dont_use_arping_lookupdev) {
                                 fprintf(stderr,
                                         "arping: Unable to automatically find "
                                         "interface to use. Is it on the local "
diff --git a/src/findif_bsdroute.c b/src/findif_bsdroute.c
index db321ff..6372145 100644
--- a/src/findif_bsdroute.c
+++ b/src/findif_bsdroute.c
@@ -1,6 +1,6 @@
 /* arping/src/findif_bsdroute.c
  *
- *  Copyright (C) 2000-2009 Thomas Habets <thomas@habets.se>
+ *  Copyright (C) 2000-2014 Thomas Habets <thomas@habets.se>
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU General Public
@@ -27,6 +27,10 @@
 #include <stdio.h>
 #include <string.h>
 
+#if HAVE_LIBNET_H
+#include <libnet.h>
+#endif
+
 #include "arping.h"
 
 /**
@@ -37,12 +41,14 @@ arping_lookupdev(uint32_t srcip,
                  uint32_t dstip,
                  char *ebuf)
 {
-	FILE *f;
+        FILE *f = NULL;
 	static char buf[10240];
 	char buf1[1024];
 	char *p,*p2;
 	int n;
 
+        *ebuf = 0;
+
         do_libnet_init(NULL, 0);
 	libnet_addr2name4_r(dstip,0,buf1, 1024);
 
@@ -52,35 +58,54 @@ arping_lookupdev(uint32_t srcip,
 	snprintf(buf, 1023, "/sbin/route -n get %s 2>&1",
 		 buf1);
 	if (!(f = popen(buf, "r"))) {
+                snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                         "popen(/sbin/route): %s", strerror(errno));
 		goto failed;
 	}
 	if (0 > (n = fread(buf, 1, sizeof(buf)-1, f))) {
-		pclose(f);
+                snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                         "fread(/sbin/route): %s", strerror(errno));
 		goto failed;
 	}
 	buf[n] = 0;
 	if (-1 == pclose(f)) {
-		perror("arping: pclose()");
+                snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                         "pclose(/sbin/route): %s", strerror(errno));
 		goto failed;
 	}
+        f = NULL;
 
 	/*
 	 * Parse interface name
 	 */
-	p = strstr(buf, "interface: ");
+        const char* head = "interface: ";
+        p = strstr(buf, head);
 	if (!p) {
+                if (verbose) {
+                        printf("arping: /sbin/route output: %s\n", buf);
+                }
+                snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                         "\"interface:\" not found in /sbin/route output.");
 		goto failed;
 	}
 
-	p+=11;
+        p += strlen(head);
 
 	p2 = strchr(p, '\n');
 	if (!p2) {
+                if (verbose) {
+                        printf("arping: /sbin/route output: %s\n", buf);
+                }
+                snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                         "interface not found in /sbin/route output.");
 		goto failed;
 	}
 	*p2 = 0;
 	return p;
  failed:
+        if (f) {
+                pclose(f);
+        }
 	return NULL;
 }
 /* ---- Emacs Variables ----
diff --git a/src/findif_getifaddrs.c b/src/findif_getifaddrs.c
index 714ceea..953289c 100644
--- a/src/findif_getifaddrs.c
+++ b/src/findif_getifaddrs.c
@@ -1,6 +1,6 @@
 /* arping/src/findif_getifaddrs.c
  *
- *  Copyright (C) 2000-2011 Thomas Habets <thomas@habets.se>
+ *  Copyright (C) 2000-2014 Thomas Habets <thomas@habets.se>
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU General Public
@@ -33,6 +33,10 @@
 #include <net/if.h>
 #include <netinet/in.h>
 
+#if HAVE_LIBNET_H
+#include <libnet.h>
+#endif
+
 #include "arping.h"
 
 const char *
@@ -52,10 +56,14 @@ arping_lookupdev(uint32_t srcip,
         /* Results */
         static char ifname[IFNAMSIZ];
 
+        *ebuf = 0;
+
         if (getifaddrs(&ifa)) {
                 if (verbose) {
                         printf("arping: getifaddrs(): %s\n", strerror(errno));
                 }
+                snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                         "getifaddrs(): %s", strerror(errno));
                 goto out;
         }
         for (cur = ifa; cur; cur = cur->ifa_next) {
@@ -94,9 +102,12 @@ arping_lookupdev(uint32_t srcip,
                         printf("arping: Autodetected interface %s\n", ret);
                 }
         } else {
-                if (verbose) {
-                        printf("Failed to find iface using getifaddrs().\n");
+                if (verbose > 1) {
+                        printf("arping: Failed to find iface using"
+                               " getifaddrs().\n");
                 }
+                snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                         "No matching interface found using getifaddrs().");
         }
  out:
         if (ifa) {
diff --git a/src/findif_linux.c b/src/findif_linux.c
index de5515d..425b6b5 100644
--- a/src/findif_linux.c
+++ b/src/findif_linux.c
@@ -1,6 +1,6 @@
 /* arping/src/findif_linux.c
  *
- *  Copyright (C) 2000-2009 Thomas Habets <thomas@habets.se>
+ *  Copyright (C) 2000-2014 Thomas Habets <thomas@habets.se>
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU General Public
@@ -27,6 +27,10 @@
 #include <stdio.h>
 #include <string.h>
 
+#if HAVE_LIBNET_H
+#include <libnet.h>
+#endif
+
 #include "arping.h"
 
 /**
@@ -37,13 +41,15 @@ arping_lookupdev(uint32_t srcip,
                  uint32_t dstip,
                  char *ebuf)
 {
-	FILE *f;
+        FILE *f = NULL;
 	static char buf[1024];
 	char buf1[1024];
 	char buf2[1024];
 	char *p,*p2;
 	int n;
 
+        *ebuf = 0;
+
         do_libnet_init(NULL, 0);
 	libnet_addr2name4_r(dstip,0,buf2,1024);
 	libnet_addr2name4_r(srcip,0,buf1,1024);
@@ -54,35 +60,54 @@ arping_lookupdev(uint32_t srcip,
 	snprintf(buf, 1023, "/sbin/ip route get %s from %s 2>&1",
 		 buf2, buf1);
 	if (!(f = popen(buf, "r"))) {
+                snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                         "popen(/sbin/ip): %s", strerror(errno));
 		goto failed;
 	}
 	if (0>(n = fread(buf, 1, sizeof(buf)-1, f))) {
-		pclose(f);
+                snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                         "fread(/sbin/ip): %s", strerror(errno));
 		goto failed;
 	}
 	buf[n] = 0;
 	if (-1 == pclose(f)) {
-		perror("arping: pclose()");
+                snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                         "pclose(/sbin/ip): %s", strerror(errno));
 		goto failed;
 	}
+        f = NULL;
 
 	/*
 	 * Parse interface name
 	 */
-	p = strstr(buf, "dev ");
+        const char* head = "dev ";
+        p = strstr(buf, head);
 	if (!p) {
+                if (verbose) {
+                        printf("arping: /sbin/ip output: %s\n", buf);
+                }
+                snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                         "\"dev \" not found in /sbin/ip output.");
 		goto failed;
 	}
 
-	p+=4;
+        p += strlen(head);
 
 	p2 = strchr(p, ' ');
 	if (!p2) {
+                if (verbose) {
+                        printf("arping: /sbin/ip output: %s\n", buf);
+                }
+                snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                         "interface not found in /sbin/ip output.");
 		goto failed;
 	}
 	*p2 = 0;
 	return p;
  failed:
+        if (f) {
+                pclose(f);
+        }
 	return NULL;
 }
 /* ---- Emacs Variables ----
diff --git a/src/findif_other.c b/src/findif_other.c
index 934be9f..917dbea 100644
--- a/src/findif_other.c
+++ b/src/findif_other.c
@@ -1,6 +1,6 @@
 /* arping/src/findif_other.c
  *
- *  Copyright (C) 2000-2009 Thomas Habets <thomas@habets.se>
+ *  Copyright (C) 2000-2014 Thomas Habets <thomas@habets.se>
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU General Public
@@ -23,6 +23,10 @@
 #include <stdio.h>
 #include <string.h>
 
+#if HAVE_LIBNET_H
+#include <libnet.h>
+#endif
+
 #include "arping.h"
 
 /**
@@ -31,6 +35,8 @@
 const char *
 arping_lookupdev(uint32_t srcip, uint32_t dstip, char *ebuf)
 {
+        snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                 "arping_lookupdev() not implemented for this system.");
 	return NULL;
 }
 /* ---- Emacs Variables ----
diff --git a/src/findif_sysctl.c b/src/findif_sysctl.c
index 7c62aaa..9874156 100644
--- a/src/findif_sysctl.c
+++ b/src/findif_sysctl.c
@@ -1,6 +1,6 @@
 /* arping/src/findif_sysctl.c
  *
- *  Copyright (C) 2000-2011 Thomas Habets <thomas@habets.se>
+ *  Copyright (C) 2000-2014 Thomas Habets <thomas@habets.se>
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU General Public
@@ -72,7 +72,8 @@ arping_lookupdev(uint32_t srcip,
         int c;
 
         /* buffer */
-        char *buf, *lim;
+        char *buf = NULL;
+        char *lim;
         size_t bufsize;
 
         /* Matching interfaces */
@@ -84,26 +85,35 @@ arping_lookupdev(uint32_t srcip,
 
         /* Results */
         static char ifName[IFNAMSIZ];
+        *ebuf = 0;
 
         /* Allocate buffer and retrieve data. */
         for (c = 0;;) {
                 if (sysctl(mib, 6, NULL, &bufsize, NULL, 0) < 0) {
-                        strcpy(ebuf, "sysctl: get buffer size error");
+                        snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                                 "sysctl: get buffer size error: %s",
+                                 strerror(errno));
                         goto failed;
                 }
                 if ((buf = malloc(bufsize)) == NULL) {
-                        strcpy(ebuf, "malloc: error");
+                        snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                                 "malloc: error: %s", strerror(errno));
                         goto failed;
                 }
                 if (sysctl(mib, 6, buf, &bufsize, NULL, 0) == 0) {
                         break;
                 }
                 if (errno != ENOMEM || ++c >= 10 ) {
-                        strcpy(ebuf, "sysctl: get ifaces error");
+                        snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                                 "sysctl: get ifaces error: %s",
+                                 strerror(errno));
                         goto failed;
                 }
-                fprintf(stderr, "sysctl: buffer size changed");
+                if (verbose > 2) {
+                        printf("sysctl: buffer size changed.");
+                }
                 free(buf);
+                buf = NULL;
         }
 
         lim = buf + bufsize;
@@ -116,7 +126,8 @@ arping_lookupdev(uint32_t srcip,
 
                 struct if_msghdr *ifh = (struct if_msghdr *)buf;
                 if (ifh->ifm_type != RTM_IFINFO) {
-                        strcpy(ebuf, "Wrong data in NET_RT_IFLIST");
+                        snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                                 "Wrong data in NET_RT_IFLIST.");
                         return NULL;
                 }
                 sdl = (struct sockaddr_dl *)(buf +
@@ -189,7 +200,7 @@ arping_lookupdev(uint32_t srcip,
 
                         match_count++;
 
-                        if (verbose) {
+                        if (verbose > 1) {
                                 printf("Specified addr matches "
                                        "interface '%s':\n", tmpIfName);
                                 printf("  IP addr %s, ",
@@ -213,24 +224,27 @@ arping_lookupdev(uint32_t srcip,
 
         if (match_count == 0 ) {
                 if (verbose) {
-                        strcpy(ebuf,
-                               "No interface found that matches specified IP");
+                        snprintf(ebuf, LIBNET_ERRBUF_SIZE,
+                                 "No interface found that matches"
+                                 " specified IP.");
                 }
                 goto failed;
         }
 
         if (verbose && match_count > 1) {
-                printf("Using interface '%s' with src IP %s due to longer "
-                       "mask.\n", ifName, inet_ntoa(best_addr));
+                printf("arping: Using interface '%s' with src IP %s due "
+                       "to longer mask.\n", ifName, inet_ntoa(best_addr));
         }
 #if 0
         if (ifce_ip != 0) {
                 *ifce_ip = best_addr.s_addr;
         }
 #endif
+        free(buf);
         return ifName;
 
  failed:
+        free(buf);
 	return NULL;
 }