ring: purge timer before we unmap tx ring buffers

If we unmap TX ring buffers and still have timer shots that trigger
the kernel to traverse the TX_RING, it can send out random crap in
some situations. Prevent this by destroying the timer and flush the
TX_RING first in wait mode.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/netsniff-ng.c b/netsniff-ng.c
index 0f97acd..ecb9e9a 100644
--- a/netsniff-ng.c
+++ b/netsniff-ng.c
@@ -131,6 +131,21 @@ static void timer_elapsed(int unused)
 	setitimer(ITIMER_REAL, &itimer, NULL);
 }
 
+static void timer_purge(void)
+{
+	int ret;
+
+	ret = pull_and_flush_tx_ring_wait(tx_sock);
+	if (unlikely(ret < 0)) {
+		if (errno != EBADF && errno != ENOBUFS)
+			panic("Flushing TX_RING failed: %s!\n", strerror(errno));
+	}
+
+	set_itimer_interval_value(&itimer, 0, 0);
+	setitimer(ITIMER_REAL, &itimer, NULL);
+}
+
+
 static void timer_next_dump(int unused)
 {
 	set_itimer_interval_value(&itimer, interval, 0);
@@ -289,6 +304,8 @@ static void pcap_to_xmit(struct ctx *ctx)
 	bug_on(gettimeofday(&end, NULL));
 	timersub(&end, &start, &diff);
 
+	timer_purge();
+
 	bpf_release(&bpf_ops);
 
 	dissector_cleanup_all();
@@ -455,6 +472,8 @@ static void receive_to_xmit(struct ctx *ctx)
 
 	out:
 
+	timer_purge();
+
 	sock_print_net_stats(rx_sock, 0);
 
 	bpf_release(&bpf_ops);