Re: libnetfilter_queue exiting on big tcp sessions

[Alessandro Vesely <vesely@tana.it>]

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On 03/Nov/10 19:35, Pablo Neira Ayuso wrote:
> On 02/11/10 16:46, Rajkumar S wrote:
>>  I am using utils/nfqnl_test.c as my test program
>
> Please, see:
>
> http://git.netfilter.org/cgi-bin/gitweb.cgi?p=libnetfilter_queue.git;a=commitdiff;h=37791b0eb98c00098a6410f6dedfdce92fc88f3e;hp=c4692e02d4fc804f7aa31f407d7d2f31861753bc

Thanks for the improved docs!

For older kernels, would it also help setting something like
-A INPUT -m limit --limit 10/second -j NFQUEUE --queue-num 0?

Would you please also amend nfqnl_test.c?  From this thread I grasp 
that packets that overflowed the queue are still received/ 
transmitted, but am unable to do better than the attached (untested) 
patch.

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--- nfqnl_test.original.c	2009-02-17 20:27:28.000000000 +0100
+++ nfqnl_test.c	2010-11-05 11:24:26.000000000 +0100
@@ -8,6 +8,8 @@
 
 #include <libnetfilter_queue/libnetfilter_queue.h>
 
+#include <errno.h>
+
 /* returns packet id */
 static u_int32_t print_pkt (struct nfq_data *tb)
 {
@@ -115,9 +117,21 @@
 
 	fd = nfq_fd(h);
 
-	while ((rv = recv(fd, buf, sizeof(buf), 0)) && rv >= 0) {
-		printf("pkt received\n");
-		nfq_handle_packet(h, buf, rv);
+	for (;;) {
+		if ((rv = recv(fd, buf, sizeof(buf), 0)) >= 0) {
+			printf("pkt received\n");
+			nfq_handle_packet(h, buf, rv);
+			continue;
+		}
+		/* if the computer is slower than the network the buffer
+		* may fill up. Depending on the application, this error
+		* may be ignored */		
+		if (errno == ENOBUFS) {
+			printf("pkt lost!!\n");
+			continue;
+		}
+		printf("recv failed: errno=%d (%s)\n",
+			errno, strerror(errno));
 	}
 
 	printf("unbinding from queue 0\n");