Author: jdp@ll.mit.edu
--- nc/netcat.c.orig	Wed May  2 15:45:17 2001
+++ nc/netcat.c	Mon May 14 14:27:25 2001
@@ -59,6 +59,14 @@
 #define RAND rand
 #endif /* HAVE_RANDOM */
 
+/* #define POSIX_SETJMP		/* If you want timeouts to work under the */
+				/* posixly correct, yet non-standard glibc-2.x*/
+				/* then define this- you may also need it for */
+				/* IRIX, and maybe some others */
+#ifdef LINUX
+#define POSIX_SETJMP
+#endif
+
 /* includes: */
 #include <sys/time.h>		/* timeval, time_t */
 #include <setjmp.h>		/* jmp_buf et al */
@@ -106,7 +117,11 @@
 #define PINF struct port_poop
 
 /* globals: */
+#ifdef POSIX_SETJMP
+sigjmp_buf jbuf;		/* timer crud */
+#else
 jmp_buf jbuf;			/* timer crud */
+#endif
 int jval = 0;			/* timer crud */
 int netfd = -1;
 int ofd = 0;			/* hexdump output fd */
@@ -232,7 +247,11 @@
   alarm (0);
   if (jval == 0)
     bail ("spurious timer interrupt!");
+#ifdef POSIX_SETJMP
+  siglongjmp (jbuf, jval);
+#else
   longjmp (jbuf, jval);
+#endif
 }
 
 /* arm :
@@ -744,12 +763,21 @@
 
 /* wrap connect inside a timer, and hit it */
   arm (1, o_wait);
+#ifdef POSIX_SETJMP
+  if (sigsetjmp (jbuf,1) == 0) {
+    rr = connect (nnetfd, (SA *)remend, sizeof (SA));
+  } else {				/* setjmp: connect failed... */
+    rr = -1;
+    errno = ETIMEDOUT;			/* fake it */
+  }
+#else
   if (setjmp (jbuf) == 0) {
     rr = connect (nnetfd, (SA *)remend, sizeof (SA));
   } else {				/* setjmp: connect failed... */
     rr = -1;
     errno = ETIMEDOUT;			/* fake it */
   }
+#endif
   arm (0, 0);
   if (rr == 0)
     return (nnetfd);
@@ -821,7 +849,8 @@
   if (o_udpmode) {
     x = sizeof (SA);		/* retval for recvfrom */
     arm (2, o_wait);		/* might as well timeout this, too */
-    if (setjmp (jbuf) == 0) {	/* do timeout for initial connect */
+#ifdef POSIX_SETJMP
+    if (sigsetjmp (jbuf,1) == 0) {	/* do timeout for initial connect */
       rr = recvfrom		/* and here we block... */
 	(nnetfd, bigbuf_net, BIGSIZ, MSG_PEEK, (SA *) remend, &x);
 Debug (("dolisten/recvfrom ding, rr = %d, netbuf %s ", rr, bigbuf_net))
@@ -842,14 +871,44 @@
     rr = connect (nnetfd, (SA *)remend, sizeof (SA));
     goto whoisit;
   } /* o_udpmode */
+#else
+    if (setjmp (jbuf) == 0) {   /* do timeout for initial connect */
+      rr = recvfrom             /* and here we block... */
+        (nnetfd, bigbuf_net, BIGSIZ, MSG_PEEK, (SA *) remend, &x);
+Debug (("dolisten/recvfrom ding, rr = %d, netbuf %s ", rr, bigbuf_net))
+    } else  
+      goto dol_tmo;             /* timeout */
+    arm (0, 0);
+/* I'm not completely clear on how this works -- BSD seems to make UDP
+   just magically work in a connect()ed context, but we'll undoubtedly run
+   into systems this deal doesn't work on.  For now, we apparently have to
+   issue a connect() on our just-tickled socket so we can write() back.
+   Again, why the fuck doesn't it just get filled in and taken care of?!
+   This hack is anything but optimal.  Basically, if you want your listener
+   to also be able to send data back, you need this connect() line, which
+   also has the side effect that now anything from a different source or even a
+   different port on the other end won't show up and will cause ICMP errors.
+   I guess that's what they meant by "connect".
+   Let's try to remember what the "U" is *really* for, eh? */
+    rr = connect (nnetfd, (SA *)remend, sizeof (SA));
+    goto whoisit;
+  } /* o_udpmode */ 
+#endif
 
 /* fall here for TCP */
   x = sizeof (SA);		/* retval for accept */
   arm (2, o_wait);		/* wrap this in a timer, too; 0 = forever */
+#ifdef POSIX_SETJMP
+  if (sigsetjmp (jbuf,1) == 0) {
+    rr = accept (nnetfd, (SA *)remend, &x);
+  } else
+    goto dol_tmo;		/* timeout */
+#else
   if (setjmp (jbuf) == 0) {
     rr = accept (nnetfd, (SA *)remend, &x);
   } else
     goto dol_tmo;		/* timeout */
+#endif
   arm (0, 0);
   close (nnetfd);		/* dump the old socket */
   nnetfd = rr;			/* here's our new one */