[PATCH libnetfilter_queue] utils: Add example of setting socket buffer size

[Duncan Roe <duncan_roe@optusnet.com.au>]

The libnetfilter_queue main HTML page mentions nfnl_rcvbufsiz() so the new
libmnl-only libnetfilter_queue will have to support it.

The added call acts as a demo and a test case.

Signed-off-by: Duncan Roe <duncan_roe@optusnet.com.au>
---
 utils/nfqnl_test.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/utils/nfqnl_test.c b/utils/nfqnl_test.c
index 682f3d7..6d2305e 100644
--- a/utils/nfqnl_test.c
+++ b/utils/nfqnl_test.c
@@ -91,6 +91,7 @@ int main(int argc, char **argv)
 	int fd;
 	int rv;
 	uint32_t queue = 0;
+	uint32_t ret;
 	char buf[4096] __attribute__ ((aligned));
 
 	if (argc == 2) {
@@ -107,6 +108,10 @@ int main(int argc, char **argv)
 		fprintf(stderr, "error during nfq_open()\n");
 		exit(1);
 	}
+	printf("setting socket buffer size to 2MB\n");
+	ret = nfnl_rcvbufsiz(nfq_nfnlh(h), 1024 * 1024);
+	printf("Read buffer set to 0x%x bytes (%gMB)\n", ret,
+	       ret / 1024.0 / 1024);
 
 	printf("unbinding existing nf_queue handler for AF_INET (if any)\n");
 	if (nfq_unbind_pf(h, AF_INET) < 0) {
-- 
2.35.8