Summary: glibc requires an explicit <resolv.h> include.
Contributor: Decklin Foster <decklin@red-bean.com>

Index: netcat-1.10/netcat.c
===================================================================
--- netcat-1.10.orig/netcat.c	2006-03-24 12:25:49.000000000 -0500
+++ netcat-1.10/netcat.c	2006-03-24 12:26:33.000000000 -0500
@@ -73,6 +73,9 @@
 #include <errno.h>
 #include <signal.h>
 #include <fcntl.h>		/* O_WRONLY et al */
+#ifdef LINUX			/* Linux needs the HERE, oh well. */
+#include <resolv.h>
+#endif
 
 /* handy stuff: */
 #define SA struct sockaddr	/* socket overgeneralization braindeath */