diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/arping.c | 68 |
1 files changed, 51 insertions, 17 deletions
diff --git a/src/arping.c b/src/arping.c index e2c157f..5e21303 100644 --- a/src/arping.c +++ b/src/arping.c @@ -626,17 +626,48 @@ strip_newline(char* s) { /** * Init libnet with specified ifname. Destroy if already inited. - * If this function retries with different parameter it will preserve - * the original error message and print that. + * + * Libnet usually needs init before we have searched for the real + * interface. In that case, first we just give a NULL pointer as the + * interface. But libnet sometimes fails to find an interface (no idea + * why), so then we try to use "lo" and "lo0" explicitly. + * + * If even loopback fails, then it'll preserve the original error + * message. + * * Call with recursive=0. */ void -do_libnet_init(const char *ifname, int recursive) +do_libnet_init(const char *inifname, int recursive) { + const char* ifname = inifname; + int last = 0; + switch (recursive) { + case 0: + break; + case 1: + ifname = "lo"; // E.g. Linux. + break; + case 2: + ifname = "lo0"; // E.g. OpenBSD. + break; + default: + last = 1; + break; + } + + // If we're given an interface name then always use that. + // No need to be recursive about it. + if (inifname != NULL && recursive == 0) { + ifname = inifname; + last = 1; + } + char ebuf[LIBNET_ERRBUF_SIZE]; ebuf[0] = 0; if (verbose > 1) { - printf("arping: libnet_init(%s)\n", ifname ? ifname : "<null>"); + printf("arping: trying libnet_init(LIBNET_LINK, %s)\n", + ifname ? ifname : "<null>"); } if (libnet) { /* Probably going to switch interface from temp to real. */ @@ -644,28 +675,31 @@ do_libnet_init(const char *ifname, int recursive) libnet = 0; } - /* Try libnet_init() even though we aren't root. We may have + /* Try libnet_init() even though we maybe aren't root. We may have * a capability or something. */ if (!(libnet = libnet_init(LIBNET_LINK, (char*)ifname, ebuf))) { strip_newline(ebuf); - if (!ifname) { - /* Sometimes libnet guesses an interface that it then - * can't use. Work around that by attempting to - * use "lo". */ - do_libnet_init("lo", 1); + if (verbose) { + fprintf(stderr, + "arping: libnet_init(LIBNET_LINK, %s): %s\n", + ifname ? ifname : "<null>", + *ebuf ? ebuf : "<no error message>"); + } + if (!last) { + do_libnet_init(ifname, recursive+1); if (libnet != NULL) { return; } - } else if (recursive) { - /* Continue original execution to get that - * error message. */ - return; } - fprintf(stderr, "arping: libnet_init(LIBNET_LINK, %s): %s\n", - ifname ? ifname : "<null>", - *ebuf ? ebuf : "<no error message>"); + if (!verbose) { + // Prevent double-print when verbose. + fprintf(stderr, + "arping: libnet_init(LIBNET_LINK, %s): %s\n", + ifname ? ifname : "<null>", + *ebuf ? ebuf : "<no error message>"); + } if (getuid() && geteuid()) { fprintf(stderr, "arping: you may need to run as root\n"); |