Add support for setting the snapshot length and not setting the filter.

Add a -s option to set the snapshot length; don't set it, even to a
default value, if -s isn't specified.

If there are no arguments specifying a filter, don't compile or install
a filter.

This allows us to test 1) whether the snapshot length works even if no
filter is set and 2) what happens if the snapshot length isn't set.

diff --git a/testprogs/writecaptest.c b/testprogs/writecaptest.c
index 5d8c16a9c814e9a5a26d3e243428fe930b7985dc..7d3177323bb981ee32d546fc23ae025503e043c0 100644 (file)
--- a/testprogs/writecaptest.c
+++ b/testprogs/writecaptest.c
@@ -76,13 +76,15 @@ stop_capture(int signum _U_)
 }
 #endif
 
-#define COMMAND_OPTIONS        "Li:w:y:"
+#define COMMAND_OPTIONS        "Li:s:w:y:"
 
 int
 main(int argc, char **argv)
 {
-       register int op;
-       register char *cp, *cmdbuf, *device, *savefile = NULL;
+       int op;
+       char *cp, *cmdbuf = NULL, *device, *end, *savefile = NULL;
+       int snaplen;
+       int snaplen_set = 0;
        pcap_if_t *devlist;
        int show_dlt_types = 0;
        int ndlts;
@@ -116,6 +118,14 @@ main(int argc, char **argv)
                        device = optarg;
                        break;
 
+               case 's':
+                       snaplen = (int)strtol(optarg, &end, 0);
+                       if (optarg == end || *end != '\0' || snaplen < 0)
+                               error("invalid snaplen %s (must be >= 0)",
+                                   optarg);
+                       snaplen_set = 1;
+                       break;
+
                case 'w':
                        savefile = optarg;
                        break;
@@ -179,10 +189,12 @@ main(int argc, char **argv)
        pd = pcap_create(device, ebuf);
        if (pd == NULL)
                error("%s", ebuf);
-       status = pcap_set_snaplen(pd, 262144);
-       if (status != 0)
-               error("%s: pcap_set_snaplen failed: %s",
+       if (snaplen_set) {
+               status = pcap_set_snaplen(pd, snaplen);
+               if (status != 0)
+                       error("%s: pcap_set_snaplen failed: %s",
                            device, pcap_statustostr(status));
+       }
        status = pcap_set_timeout(pd, 100);
        if (status != 0)
                error("%s: pcap_set_timeout failed: %s",
@@ -216,13 +228,21 @@ main(int argc, char **argv)
                        error("%s: %s", device, pcap_geterr(pd));
        }
 
-       cmdbuf = copy_argv(&argv[optind]);
+       /*
+        * Don't set a filter unless we were given one on the
+        * command line; if capturing doesn't work, or doesn't
+        * use the snapshot length, without a filter, that's
+        * a bug.
+        */
+       if (optind < argc) {
+               cmdbuf = copy_argv(&argv[optind]);
 
-       if (pcap_compile(pd, &fcode, cmdbuf, 1, netmask) < 0)
-               error("%s", pcap_geterr(pd));
+               if (pcap_compile(pd, &fcode, cmdbuf, 1, netmask) < 0)
+                       error("%s", pcap_geterr(pd));
 
-       if (pcap_setfilter(pd, &fcode) < 0)
-               error("%s", pcap_geterr(pd));
+               if (pcap_setfilter(pd, &fcode) < 0)
+                       error("%s", pcap_geterr(pd));
+       }
 
        pdd = pcap_dump_open(pd, savefile);
        if (pdd == NULL)
@@ -276,15 +296,17 @@ main(int argc, char **argv)
                    program_name, pcap_geterr(pd));
        }
        pcap_close(pd);
-       pcap_freecode(&fcode);
-       free(cmdbuf);
+       if (cmdbuf != NULL) {
+               pcap_freecode(&fcode);
+               free(cmdbuf);
+       }
        exit(status == -1 ? 1 : 0);
 }
 
 static void
 usage(void)
 {
-       (void)fprintf(stderr, "Usage: %s -L [ -i interface ] [ -w file ] [ -y dlt ] [expression]\n",
+       (void)fprintf(stderr, "Usage: %s -L [ -i interface ] [ -s snaplen ] [ -w file ] [ -y dlt ] [expression]\n",
            program_name);
        exit(1);
 }