From: Guy Harris <guy@alum.mit.edu>
Date: Fri, 13 May 2011 07:24:42 +0000 (-0700)
Subject: Handle kernels that don't support PACKET_RESERVE.
X-Git-Tag: libpcap-1.2.1~56
X-Git-Url: https://git.tcpdump.org/libpcap/commitdiff_plain/c3e4329535c3de5b66c418d79f34ac9ea8eae1e2

Handle kernels that don't support PACKET_RESERVE.

If, for some reason, the header files define PACKET_RESERVE but the
kernel fails with ENOPROTOOPT if we use it in getsockopt(), treat it the
same way we treat systems that don't define PACKET_RESERVE in the first
place.  One might argue that this "can't happen", but it apparently did
happen in Debian bug 625443:

	http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=625443
---

diff --git a/pcap-linux.c b/pcap-linux.c
index a72aecdc..245c4859 100644
--- a/pcap-linux.c
+++ b/pcap-linux.c
@@ -3223,9 +3223,17 @@ create_ring(pcap_t *handle, int *status)
 #ifdef PACKET_RESERVE
 	len = sizeof(tp_reserve);
 	if (getsockopt(handle->fd, SOL_PACKET, PACKET_RESERVE, &tp_reserve, &len) < 0) {
-		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "getsockopt: %s", pcap_strerror(errno));
-		*status = PCAP_ERROR;
-		return -1;
+		if (errno != ENOPROTOOPT) {
+			/*
+			 * ENOPROTOOPT means "kernel doesn't support
+			 * PACKET_RESERVE", in which case we fall back
+			 * as best we can.
+			 */
+			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "getsockopt: %s", pcap_strerror(errno));
+			*status = PCAP_ERROR;
+			return -1;
+		}
+		tp_reserve = 0;	/* older kernel, reserve not supported */
 	}
 #else
 	tp_reserve = 0;	/* older kernel, reserve not supported */