bin/50248: tcpdump -w don't work.

[nonakap%gmail.com@localhost]

>Number:         50248
>Category:       bin
>Synopsis:       tcpdump -w don't work.
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Sep 15 08:30:00 +0000 2015
>Originator:     NONAKA Kimihiro
>Release:        HEAD 20150915
>Organization:
>Environment:
NetBSD netbsd 7.99.21 NetBSD 7.99.21 (KOHARU) #41: Tue Sep 15 12:08:42 JST 2015  nonaka@netbsd:/home/snapshot/NetBSD/HEAD.20150827/obj.NetBSD-amd64/amd64/sys/arch/amd64/compile/KOHARU amd64
>Description:
# tcpdump -w xxx.pcap
tcpdump: xxx.pcap: Permission denied
# tcpdump -w ~/xxx.pcap
tcpdump: /home/nonaka/xxx.pcap: No such file or directory

Failed to open the xxx.pcap file because try it after chroot(2).

>How-To-Repeat:
tcpdump -w xxx.pcap
>Fix:
Re-apply src/external/bsd/tcpdump/dist/tcpdump.c rev.1.8.

diff --git a/external/bsd/tcpdump/dist/tcpdump.c b/external/bsd/tcpdump/dist/tcpdump.c
index 2555495..009f294 100644
--- a/external/bsd/tcpdump/dist/tcpdump.c
+++ b/external/bsd/tcpdump/dist/tcpdump.c
@@ -1857,6 +1857,9 @@ main(int argc, char **argv)
 		capng_apply(CAPNG_SELECT_BOTH);
 #endif /* HAVE_LIBCAP_NG */
 		if (username || chroot_dir)
+#ifndef HAVE_LIBCAP_NG
+			if (!WFileName)
+#endif
 			droproot(username, chroot_dir);
 	}
 #endif /* WIN32 */