Add a routine to format error messages with an errno-based message at the end.

That routine will use strerror_s() or strerror_r() if available, in a
fashion that's thread-safe.  Otherwise, it falls back on
pcap_strerror().

Use it in both libpcap and rpcapd.

Given that we check for errors in strerror_r(), hopefully this will
squelch warnings with newer version of GCC and GNU libc; whilst the
macOS (and other BSD-flavored?) strerror_r() always fills in a message,
that's not required by the Single UNIX Specification, as far as I can
tell, so we apparently really *do* need to check for errors.

1 files changed, 3 insertions, 3 deletions

diff --git a/pcap-netmap.c b/pcap-netmap.c
index 00e6e414..ee8d8b3a 100644
--- a/pcap-netmap.c
+++ b/pcap-netmap.c
@@ -193,9 +193,9 @@ pcap_netmap_activate(pcap_t *p)
 
 	d = nm_open(p->opt.device, NULL, 0, NULL);
 	if (d == NULL) {
-		pcap_snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
-			"netmap open: cannot access %s: %s\n",
-			p->opt.device, pcap_strerror(errno));
+		pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
+		    errno, "netmap open: cannot access %s",
+		    p->opt.device);
 		pcap_cleanup_live_common(p);
 		return (PCAP_ERROR);
 	}