Improve error messages from bpf_open(), and let it do the error handling.

[libpcap] / pcap-bpf.c

diff --git a/pcap-bpf.c b/pcap-bpf.c
index 1d2fe17923ab3b87125f6da08894298797b41a46..0dfdf39a75dbd596dcec6fce83c88c37cdd31677 100644 (file)
--- a/pcap-bpf.c
+++ b/pcap-bpf.c
@@ -435,6 +435,10 @@ pcap_create(const char *device, char *ebuf)
        return (p);
 }
 
+/*
+ * On success, returns a file descriptor for a BPF device.
+ * On failure, returns a PCAP_ERROR_ value, and sets p->errbuf.
+ */
 static int
 bpf_open(pcap_t *p)
 {
@@ -495,12 +499,52 @@ bpf_open(pcap_t *p)
         * XXX better message for all minors used
         */
        if (fd < 0) {
-               if (errno == EACCES)
+               switch (errno) {
+
+               case ENOENT:
+                       fd = PCAP_ERROR;
+                       if (n == 1) {
+                               /*
+                                * /dev/bpf0 doesn't exist, which
+                                * means we probably have no BPF
+                                * devices.
+                                */
+                               snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
+                                   "(there are no BPF devices)");
+                       } else {
+                               /*
+                                * We got EBUSY on at least one
+                                * BPF device, so we have BPF
+                                * devices, but all the ones
+                                * that exist are busy.
+                                */
+                               snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
+                                   "(all BPF devices are busy)");
+                       }
+                       break;
+
+               case EACCES:
+                       /*
+                        * Got EACCES on the last device we tried,
+                        * and EBUSY on all devices before that,
+                        * if any.
+                        */
                        fd = PCAP_ERROR_PERM_DENIED;
-               else
+                       snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
+                           "(cannot open BPF device) %s: %s", device,
+                           pcap_strerror(errno));
+                       break;
+
+               default:
+                       /*
+                        * Some other problem.
+                        */
                        fd = PCAP_ERROR;
-               snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "(no devices found) %s: %s",
-                   device, pcap_strerror(errno));
+                       snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
+                           "(cannot open BPF device) %s: %s", device,
+                           pcap_strerror(errno));
+                       break;
+               }
        }
 #endif
 
@@ -672,19 +716,8 @@ pcap_can_set_rfmon_bpf(pcap_t *p)
         * First, open a BPF device.
         */
        fd = bpf_open(p);
-       if (fd < 0) {
-               if (errno == EACCES) {
-                       /*
-                        * Sorry, you don't have permission to do capturing.
-                        */
-                       return (PCAP_ERROR_PERM_DENIED);
-               } else {
-                       snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
-                           "Can't open BPF device for %s: %s",
-                           p->opt.source, pcap_strerror(errno));
-                       return (PCAP_ERROR);
-               }
-       }
+       if (fd < 0)
+               return (fd);    /* fd is the appropriate error code */
 
        /*
         * Now bind to the device.