Report periodic stats only when safe to do so. [skip ci]
As explained in GH #155, when tcpdump is given -r, -w and -v and it
takes long enough to read from the input file (because it is stdin
connected through network or a pipe to stdout of another tcpdump doing
a live capture), pcap_loop() will error before long. One of the ways to
reproduce the fault is as follows:
$ tcpdump -i eno1 -w - | tcpdump -r - -w /tmp/tmp.pcap -v
tcpdump: listening on eno1, link-type EN10MB (Ethernet), snapshot length 262144 bytes
reading from file -, link-type EN10MB (Ethernet), snapshot length 262144
tcpdump: pcap_loop: error reading dump file: Interrupted system call
Skip the verbose_stats_dump() timer setup in this specific corner case
for the time being and document it.
diff --git a/tcpdump.1.in b/tcpdump.1.in
index 7f716ab..bf4d7b2 100644
--- a/tcpdump.1.in
+++ b/tcpdump.1.in
@@ -20,7 +20,7 @@
.\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
.\"
-.TH TCPDUMP 1 "10 Aug 2020"
+.TH TCPDUMP 1 "29 Aug 2020"
.SH NAME
tcpdump \- dump traffic on a network
.SH SYNOPSIS
@@ -808,6 +808,8 @@
.IP
When writing to a file with the
.B \-w
+option and at the same time not reading from a file with the
+.B \-r
option, report, once per second, the number of packets captured.
.TP
.B \-vv
diff --git a/tcpdump.c b/tcpdump.c
index 939df0b..d5d35ff 100644
--- a/tcpdump.c
+++ b/tcpdump.c
@@ -2438,11 +2438,14 @@
(void)setsignal(SIGNAL_FLUSH_PCAP, flushpcap);
#endif
- if (ndo->ndo_vflag > 0 && WFileName && !print) {
+ if (ndo->ndo_vflag > 0 && WFileName && RFileName == NULL && !print) {
/*
* When capturing to a file, if "--print" wasn't specified,
*"-v" means tcpdump should, once per second,
* "v"erbosely report the number of packets captured.
+ * Except when reading from a file, because -r, -w and -v
+ * together used to make a corner case, in which pcap_loop()
+ * errored due to EINTR (see GH #155 for details).
*/
#ifdef _WIN32
/*
