Return an appropriate error message for ERROR_GEN_FAILURE when capturing.

That's the error returned if the capture stops working because either 1)
the device was removed (unplugged) or 2) the device becomes unusable for
capturing due to a suspend/resume.

diff --git a/pcap-npf.c b/pcap-npf.c
index a9a1967f6fbd1112d6b0804a8a6a57fdf0181b32..15018da9c3903c8e7082318816b0f0c4c2a1eb18 100644 (file)
--- a/pcap-npf.c
+++ b/pcap-npf.c
@@ -523,7 +523,34 @@ pcap_read_npf(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
                 */
                PacketInitPacket(&Packet, (BYTE *)p->buffer, p->bufsize);
                if (!PacketReceivePacket(pw->adapter, &Packet, TRUE)) {
-                       pcap_snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "read error: PacketReceivePacket failed");
+                       /*
+                        * Did the device go away?
+                        * If so, the error we get is ERROR_GEN_FAILURE.
+                        */
+                       DWORD errcode = GetLastError();
+
+                       if (errcode == ERROR_GEN_FAILURE) {
+                               /*
+                                * The device on which we're capturing
+                                * went away, or it became unusable
+                                * by NPF due to a suspend/resume.
+                                *
+                                * XXX - hopefully no other error
+                                * conditions are indicated by this.
+                                *
+                                * XXX - we really should return an
+                                * appropriate error for that, but
+                                * pcap_dispatch() etc. aren't
+                                * documented as having error returns
+                                * other than PCAP_ERROR or PCAP_ERROR_BREAK.
+                                */
+                               pcap_snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
+                                   "The interface disappeared");
+                       } else {
+                               pcap_fmt_errmsg_for_win32_err(p->errbuf,
+                                   PCAP_ERRBUF_SIZE, errcode,
+                                   "PacketReceivePacket error");
+                       }
                        return (PCAP_ERROR);
                }