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Note by jsynacek:
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This patch should be rewritten. There's no reason to be using a static variable
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and returning its content from a function (in iterate_dev()). Also, some things
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should be simplified (like iterate_dev()).
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diff -up ./arpwatch.c.iselect ./arpwatch.c
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--- ./arpwatch.c.iselect 2012-10-15 16:01:24.701335291 +0200
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+++ ./arpwatch.c 2012-10-15 16:07:18.626322639 +0200
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@@ -162,50 +162,52 @@ void dropprivileges(const char* user)
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}
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char *
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-get_first_dev(pcap_t **pd, int *linktype, char *errbuf)
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+try_dev(char *interface, pcap_t **pd, int *linktype, char *errbuf)
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{
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- static char interface[IF_NAMESIZE + 1];
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register int snaplen, timeout;
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- pcap_if_t *alldevs;
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- pcap_if_t *dev;
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- char *ret = NULL;
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snaplen = max(sizeof(struct ether_header),
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sizeof(struct fddi_header)) + sizeof(struct ether_arp);
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timeout = 1000;
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- if (pcap_findalldevs(&alldevs, errbuf) == -1) {
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- (void)fprintf(stderr, "%s: lookup_device: %s\n",
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- prog, errbuf);
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- exit(1);
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+ *pd = pcap_open_live(interface, snaplen, 1, timeout, errbuf);
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+ if (NULL == *pd) {
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+ syslog(LOG_ERR, "pcap open %s: %s", interface, errbuf);
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+ return NULL;
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}
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+ *linktype = pcap_datalink(*pd);
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+ /* Must be ethernet or fddi */
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+ if (*linktype != DLT_EN10MB && *linktype != DLT_FDDI) {
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+ syslog(LOG_ERR, "(%s) Link layer type %d not ethernet or fddi",
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+ interface, *linktype);
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+ pcap_close(*pd);
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+ return NULL;
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+ }
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+ return interface;
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+}
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- for (dev = alldevs; dev; dev = dev->next) {
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- strncpy(interface, dev->name, strlen(dev->name)+1);
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-
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- *pd = pcap_open_live(interface, snaplen, 1, timeout, errbuf);
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- if (*pd == NULL) {
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- syslog(LOG_ERR, "pcap open %s: %s, trying next...", interface, errbuf);
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- continue;
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- /* exit(1); */
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- }
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+char *
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+iterate_dev(char *arginterface, pcap_t **pd, int *linktype, char *errbuf)
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+{
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+ static char interface[64 + 1];
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+ pcap_if_t *alldevs;
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+ pcap_if_t *dev;
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- *linktype = pcap_datalink(*pd);
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- /* Must be ethernet or fddi */
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- if (*linktype != DLT_EN10MB && *linktype != DLT_FDDI) {
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- syslog(LOG_ERR, "(%s) Link layer type %d not ethernet or fddi, trying next...",
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- interface, *linktype);
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- pcap_close(*pd);
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+ if (NULL != arginterface) {
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+ return try_dev(arginterface, pd, linktype, errbuf);
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+ } else {
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+ if (pcap_findalldevs(&alldevs, errbuf) == -1) {
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+ (void)fprintf(stderr, "%s: lookup_device: %s\n",
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+ prog, errbuf);
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+ exit(1);
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}
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- else {
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- /* First match, use it */
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- ret = interface;
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- break;
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+ for (dev = alldevs; dev && (arginterface == NULL); dev = dev->next) {
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+ strncpy(interface, dev->name, strlen(dev->name)+1);
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+ arginterface = try_dev(interface, pd, linktype, errbuf);
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}
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-
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+ pcap_freealldevs(alldevs);
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+ return arginterface;
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}
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- pcap_freealldevs(alldevs);
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- return (ret);
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}
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int
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@@ -315,8 +317,8 @@ main(int argc, char **argv)
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} else {
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/* Determine interface if not specified */
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- if (interface == NULL &&
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- (interface = get_first_dev(&pd, &linktype, errbuf)) == NULL) {
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+ interface = iterate_dev(interface, &pd, &linktype, errbuf);
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+ if (interface == NULL) {
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(void)fprintf(stderr, "%s: lookup_device: no suitable interface found\n",
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prog);
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exit(1);
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