https://sourceforge.net/tracker/?func=detail&aid=3120897&group_id=53066&atid=469575

From 6f8927c609d1f986a45010b7acae0eb570668642 Mon Sep 17 00:00:00 2001
From: Mike Frysinger <vapier@gentoo.org>
Date: Sat, 27 Nov 2010 17:18:05 -0500
Subject: [PATCH] add support for nommu systems

Rather than hardcode the WIN32 define, add proper fork checks to the
configure script and check those.  This fixes building for nommu systems
which lack the fork function.

While we're here though, add support for this functionality via vfork
so that it does work on nommu systems.  And fix an old bug where we
exit properly in the forked child when the exec failed instead of just
returning to the calling code (which isn't expecting it).

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
---

--- tcpdump-4.0.0/config.h.in
+++ tcpdump-4.0.0/config.h.in
@@ -151,6 +151,9 @@
 /* Define to 1 if you have the <fcntl.h> header file. */
 #undef HAVE_FCNTL_H
 
+/* Define to 1 if you have the `fork' function. */
+#undef HAVE_FORK
+
 /* Define to 1 if you have the `getnameinfo' function. */
 #undef HAVE_GETNAMEINFO
 
@@ -274,6 +277,9 @@
 /* Define to 1 if you have the <unistd.h> header file. */
 #undef HAVE_UNISTD_H
 
+/* Define to 1 if you have the `vfork' function. */
+#undef HAVE_VFORK
+
 /* Define to 1 if you have the `vfprintf' function. */
 #undef HAVE_VFPRINTF
 
--- tcpdump-4.0.0/configure
+++ tcpdump-4.0.0/configure
@@ -7976,7 +7976,7 @@ done
 
 
 
-for ac_func in strftime
+for ac_func in fork vfork strftime
 do
 as_ac_var=`echo "ac_cv_func_$ac_func" | $as_tr_sh`
 { echo "$as_me:$LINENO: checking for $ac_func" >&5
diff --git a/tcpdump.c b/tcpdump.c
index c8da36b..abf3e69 100644
--- a/tcpdump.c
+++ b/tcpdump.c
@@ -1250,8 +1250,10 @@ main(int argc, char **argv)
 	(void)setsignal(SIGPIPE, cleanup);
 	(void)setsignal(SIGTERM, cleanup);
 	(void)setsignal(SIGINT, cleanup);
-	(void)setsignal(SIGCHLD, child_cleanup);
 #endif /* WIN32 */
+#if defined(HAVE_FORK) || defined(HAVE_VFORK)
+	(void)setsignal(SIGCHLD, child_cleanup);
+#endif
 	/* Cooperate with nohup(1) */
 #ifndef WIN32	
 	if ((oldhandler = setsignal(SIGHUP, cleanup)) != SIG_DFL)
@@ -1464,13 +1466,13 @@ cleanup(int signo _U_)
   On windows, we do not use a fork, so we do not care less about
   waiting a child processes to die
  */
-#ifndef WIN32
+#if defined(HAVE_FORK) || defined(HAVE_VFORK)
 static RETSIGTYPE
 child_cleanup(int signo _U_)
 {
   wait(NULL);
 }
-#endif /* WIN32 */
+#endif /* HAVE_FORK || HAVE_VFORK */
 
 static void
 info(register int verbose)
@@ -1514,11 +1516,15 @@ info(register int verbose)
 	infoprint = 0;
 }
 
-#ifndef WIN32
+#if defined(HAVE_FORK) || defined(HAVE_VFORK)
 static void
 compress_savefile(const char *filename)
 {
+# ifdef HAVE_FORK
 	if (fork())
+# else
+	if (vfork())
+# endif
 		return;
 	/*
 	 * Set to lowest priority so that this doesn't disturb the capture
@@ -1534,15 +1540,20 @@ compress_savefile(const char *filename)
 			zflag,
 			filename,
 			strerror(errno));
+# ifdef HAVE_FORK
+	exit(1);
+# else
+	_exit(1);
+# endif
 }
-#else  /* WIN32 */
+#else  /* HAVE_FORK || HAVE_VFORK */
 static void
 compress_savefile(const char *filename)
 {
 	fprintf(stderr,
-		"compress_savefile failed. Functionality not implemented under windows\n");
+		"compress_savefile failed. Functionality not implemented under your system\n");
 }
-#endif /* WIN32 */
+#endif /* HAVE_FORK || HAVE_VFORK */
 
 static void
 dump_packet_and_trunc(u_char *user, const struct pcap_pkthdr *h, const u_char *sp)
-- 
1.7.3.1