When sniffing on the loopback device, each packet will be seen
twice, once per direction. To avoid duplicates, explicitly
skip OUTGOING packets received from loopback, if no packet_type
filter is explicitly set.
Signed-off-by: Paolo Abeni <pab...@redhat.com>
---
netsniff-ng.c | 32 ++++++++++++++++++++++----------
1 file changed, 22 insertions(+), 10 deletions(-)
diff --git a/netsniff-ng.c b/netsniff-ng.c
index 8d22151..4cfabc1 100644
--- a/netsniff-ng.c
+++ b/netsniff-ng.c
@@ -55,7 +55,7 @@ enum dump_mode {
struct ctx {
char *device_in, *device_out, *device_trans, *filter, *prefix;
- int cpu, rfraw, dump, print_mode, dump_dir, packet_type;
+ int cpu, rfraw, dump, print_mode, dump_dir, packet_type, lo_ifindex;
unsigned long kpull, dump_interval, tx_bytes, tx_packets;
size_t reserve_size;
bool randomize, promiscuous, enforce, jumbo, dump_bpf, hwtimestamp,
verbose;
@@ -410,6 +410,18 @@ out:
printf("\r%12lu sec, %lu usec in total\n", diff.tv_sec, diff.tv_usec);
}
+static inline bool skip_packet(struct ctx *ctx, struct sockaddr_ll *sll)
+{
+ if (ctx->packet_type != -1)
+ return ctx->packet_type != sll->sll_pkttype;
+
+ /* when receving from the loopback device, each packet is seen twice,
+ * so drop the outgoing ones to avoid duplicates
+ */
+ return (sll->sll_ifindex == ctx->lo_ifindex) &&
+ (sll->sll_pkttype == PACKET_OUTGOING);
+}
+
static void receive_to_xmit(struct ctx *ctx)
{
short ifflags = 0;
@@ -470,9 +482,8 @@ static void receive_to_xmit(struct ctx *ctx)
ctx->pkts_seen++;
- if (ctx->packet_type != -1)
- if (ctx->packet_type !=
hdr_in->s_ll.sll_pkttype)
- goto next;
+ if (skip_packet(ctx, &hdr_in->s_ll))
+ goto next;
hdr_out = tx_ring.frames[it_out].iov_base;
out = ((uint8_t *) hdr_out) + TPACKET2_HDRLEN -
sizeof(struct sockaddr_ll);
@@ -942,9 +953,8 @@ static void walk_t3_block(struct block_desc *pbd, struct
ctx *ctx,
uint8_t *packet = ((uint8_t *) hdr + hdr->tp_mac);
pcap_pkthdr_t phdr;
- if (ctx->packet_type != -1)
- if (ctx->packet_type != sll->sll_pkttype)
- goto next;
+ if (skip_packet(ctx, sll))
+ goto next;
ctx->pkts_seen++;
@@ -1071,9 +1081,8 @@ static void recv_only_or_dump(struct ctx *ctx)
uint8_t *packet = ((uint8_t *) hdr) + hdr->tp_h.tp_mac;
pcap_pkthdr_t phdr;
- if (ctx->packet_type != -1)
- if (ctx->packet_type != hdr->s_ll.sll_pkttype)
- goto next;
+ if (skip_packet(ctx, &hdr->s_ll))
+ goto next;
ctx->pkts_seen++;
@@ -1523,6 +1532,9 @@ int main(int argc, char **argv)
if (!ctx.device_in)
ctx.device_in = xstrdup("any");
+ if (!strcmp(ctx.device_in, "any") || !strcmp(ctx.device_in, "lo"))
+ ctx.lo_ifindex = device_ifindex("lo");
+
register_signal(SIGINT, signal_handler);
register_signal(SIGQUIT, signal_handler);
register_signal(SIGTERM, signal_handler);
--
1.8.3.1
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