Dumpcap: print closed ring-buffer file names

This proposal adds a new option '-b printname:<filename>' to dumpcap. If
used, dumpcap will print the name of each ring buffer file it creates
after it is closed. Allows the use of '-'/'stdout' and 'stderr'.

Use case: Since the file name is printed after the file is closed for
writing, an automated capture process can do something like the
following with the guarantee that the file in question will not be
changed.

    dumpcap -i eth0 -b files:2 -b printname:stdout [-b ...] | \
    while read cap_file_name ; do
        # Do something with $cap_file_name
    done

This sort of scripting is difficult in dumpcap's current form. Dumpcap
prints the names of new files to stderr as it *opens* them, so a script
attempting to use this must sleep for "-b duration:value" seconds plus
some fudge time to be sure it's getting a closed, unchanging file.

Change-Id: Idb288cc7c8c30443256d35c8cd4460a2e3f0861c
Reviewed-on: https://code.wireshark.org/review/37994
Petri-Dish: Alexis La Goutte <alexis.lagoutte@gmail.com>
Tested-by: Petri Dish Buildbot
Reviewed-by: Anders Broman <a.broman58@gmail.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/capture_opts.c b/capture_opts.c
index 5d4ed86355..05a8e67897 100644
--- a/capture_opts.c
+++ b/capture_opts.c
@@ -116,6 +116,8 @@ capture_opts_init(capture_options *capture_opts)
 
     capture_opts->output_to_pipe                  = FALSE;
     capture_opts->capture_child                   = FALSE;
+    capture_opts->print_file_names                = FALSE;
+    capture_opts->print_name_to                   = NULL;
 }
 
 void
@@ -248,6 +250,7 @@ capture_opts_log(const char *log_domain, GLogLevelFlags log_level, capture_optio
     g_log(log_domain, log_level, "FileInterval    (%u) : %u", capture_opts->has_file_interval, capture_opts->file_interval);
     g_log(log_domain, log_level, "FilePackets     (%u) : %u", capture_opts->has_file_packets, capture_opts->file_packets);
     g_log(log_domain, log_level, "RingNumFiles    (%u) : %u", capture_opts->has_ring_num_files, capture_opts->ring_num_files);
+    g_log(log_domain, log_level, "RingPrintFiles  (%u) : %s", capture_opts->print_file_names, (capture_opts->print_file_names ? capture_opts->print_name_to : ""));
 
     g_log(log_domain, log_level, "AutostopFiles   (%u) : %u", capture_opts->has_autostop_files, capture_opts->autostop_files);
     g_log(log_domain, log_level, "AutostopPackets (%u) : %u", capture_opts->has_autostop_packets, capture_opts->autostop_packets);
@@ -411,6 +414,9 @@ get_ring_arguments(capture_options *capture_opts, const char *arg)
     } else if (strcmp(arg,"packets") == 0) {
         capture_opts->has_file_packets = TRUE;
         capture_opts->file_packets = get_positive_int(p, "ring buffer packet count");
+    } else if (strcmp(arg,"printname") == 0) {
+        capture_opts->print_file_names = TRUE;
+        capture_opts->print_name_to = g_strdup(p);
     }
 
     *colonp = ':';    /* put the colon back */