From 2d6e537e609bad84996847ab5ea6b59bf4bc6773 Mon Sep 17 00:00:00 2001
From: Guy Harris <gharris@sonic.net>
Date: Fri, 14 Aug 2020 18:29:33 -0700
Subject: [PATCH] Improve error reporting.

The return value of pcap_activate() is:

	0, if activation succeeded, with no warnings;
	a non-zero positive number, if activation succeded with a
	    warning - the number is a PCAP_WARNING_ indication of the
	    warning;
	a negative number, if activation failed - the number is a
	    PCAP_ERROR_ indication of the error.

We should not treat non-zero positive numbers as errors.  (Printing a
warning might be useful.)

We should treat non-zero negative numbers as errors, and translate it to
an error message using libpcap's own pcap_statustostr(), rather than
attempting to duplicate its mapping ourselves, as new error codes may
appear in the future, and using pcap_statustostr() future-proofs us
against that.  In addition, if the error is PCAP_ERROR, we should report
the return value of pcap_geterr(handle), as that will provide additional
information about that "generic" error.
---
 src/init.c | 35 ++++++++++++++++-------------------
 1 file changed, 16 insertions(+), 19 deletions(-)

diff --git a/src/init.c b/src/init.c
index 587b0d6..c26ec7a 100644
--- a/src/init.c
+++ b/src/init.c
@@ -143,30 +143,27 @@ pcap_t *capture_init(char *capture_source)
 		pcap_set_timeout(handle, 50);
 		pcap_set_rfmon(handle, activate_rfmon);
 		pcap_set_promisc(handle, 1);
-		if(!(status = pcap_activate(handle)))
+		status = pcap_activate(handle);
+		if(status >= 0) {
+			// Complete success, or success with warning.
+			// XXX - report warning?
 			return handle;
+		}
 		if(status == PCAP_ERROR_RFMON_NOTSUP) {
 			pcap_set_rfmon(handle, 0);
 			status = pcap_activate(handle);
-			if(!status) return handle;
+			if(status >= 0) {
+				// Complete success, or success with warning.
+				// XXX - report warning?
+				return handle;
+			}
+		}
+		if(status < 0) {
+			if(status == PCAP_ERROR)
+				cprintf(CRITICAL, "[X] ERROR: pcap_activate status %d - %s, %s\n", status, pcap_statustostr(status), pcap_geterr(handle));
+			else
+				cprintf(CRITICAL, "[X] ERROR: pcap_activate status %d - %s\n", status, pcap_statustostr(status));
 		}
-		cprintf(CRITICAL, "[X] ERROR: pcap_activate status %d\n", status);
-		static const char *pcap_errmsg[] = {
-			[1] = "generic error code",
-			[2] = "loop terminated by pcap_breakloop",
-			[3] = "the capture needs to be activated",
-			[4] = "the operation can't be performed on already activated captures",
-			[5] = "no such device exists",
-			[6] = "this device doesn't support rfmon (monitor) mode",
-			[7] = "operation supported only in monitor mode",
-			[8] = "no permission to open the device",
-			[9] = "interface isn't up",
-			[10]= "this device doesn't support setting the time stamp type",
-			[11]= "you don't have permission to capture in promiscuous mode",
-			[12]= "the requested time stamp precision is not supported",
-		};
-		if(status < 0 && status > -13)
-			cprintf(CRITICAL, "[X] PCAP: %s\n", pcap_errmsg[-status]);
 		pcap_close(handle);
 		handle = 0;
 	}