add a ping-pong mode.  correct a few stupids.  add an argument to die() to
explain what the error was.

Reference: /n/atom/patch/applied/nettest-pingpong
Date: Sun May 10 18:25:43 CES 2015
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/nettest.c	Sun May 10 18:24:52 2015
+++ /sys/src/cmd/nettest.c	Sun May 10 18:24:53 2015
@@ -12,31 +12,30 @@
 		"01234567890abcdef01234567890abcdef01234567890abcdef01234567890abcdef"
 		"01234567890abcdef01234567890abcdef01234567890abcdef01234567890abcdef";
 
-
 uchar	flag[127];
-ulong	n;
-long	sleepms;
-vlong	sleepns;
+uint	n;
+uint	sleepms;
 
 #define dprint(...) {if(flag['d']) print(__VA_ARGS__);}
 
 enum {
 	Blen = 8*1024,
+	Rlen = 64,
 };
 
 void
 usage(void)
 {
-	fprint(2, "usage: %s [-l] [-t [-h halg -e encalg]] [-s sleepms] [-n nblocks]\n"
-		"	%s  [-t [-h halg -e encalg]] [-a addr] [-s sleepms]\n"
-		"	%s  [-t [-h halg -e encalg]] -r addr -n nblocks\n", argv0, argv0, argv0);
+	fprint(2, "usage: %s -l [-dp] [-t [-h halg -e encalg]] [-s sleepms] [-n nblocks]\n"
+		"	%s [-dp] [-t [-h halg -e encalg]] [-a addr] [-s sleepms]\n"
+		"	%s [-dp] [-t [-h halg -e encalg]] -r addr -n nblocks\n", argv0, argv0, argv0);
 	exits("usage");
 }
 
 void
-die(void)
+die(char *s)
 {
-	sysfatal("%s: %r", argv0);
+	sysfatal("%s: %s: %r", argv0, s);
 }
 
 int
@@ -65,7 +64,7 @@
 void
 client(void)
 {
-	char *dst, b[Blen];
+	char *dst, b[Blen], r[Rlen];
 	int fd, i;
 
 	atnotify(notef, 1);
@@ -74,7 +73,7 @@
 	dst = ·netmkaddr(raddr, "tcp", service);
 	alarm(3*1000);
 	if((fd = dial(dst, 0, 0, 0)) < 0)
-		die();
+		die("dial");
 	alarm(0);
 	free(dst);
 	dprint("dialed\n");
@@ -84,8 +83,10 @@
 			sysfatal("client: pushtls %r");
 	}
 	for(i = 0; i < n; ++i){
-		if(write(fd, b, sizeof b) < 0)
-			die();
+		if(write(fd, b, sizeof b) == -1)
+			die("write");
+		if(flag['p'] && readn(fd, r, sizeof r) != sizeof r)
+			die("read");
 	}
 	close(fd);
 	dprint("wrote\n");
@@ -95,8 +96,8 @@
 server(void)
 {
 	int acfd, lcfd, dfd;
-	char adir[40], ldir[40], b[Blen], *a;
-	long c;
+	char adir[40], ldir[40], b[Blen], r[Rlen], *a;
+	int c;
 	uvlong i, t;
 	double ratemb, maxr, delta;
 	NetConnInfo *nc;
@@ -105,15 +106,15 @@
 	a = ·netmkaddr(laddr, "tcp", service);
 	acfd = announce(a, adir);
 	if(acfd == -1)
-		die();
+		die("announce");
 	free(a);
 
 	dprint("listen\n");
 	if((lcfd = listen(adir, ldir)) < 0)
-		die();
+		die("listen");
 	dprint("listened\n");
 	if((dfd = accept(lcfd, ldir)) < 0)
-		die();
+		die("accept");
 	nc = getnetconninfo(ldir, dfd);
 	dprint("accepted\n");
 	if(flag['t']){
@@ -126,6 +127,8 @@
 		c = readn(dfd, b, sizeof b);
 		if(c != sizeof b)
 			break;
+		if(flag['p'] && write(dfd, r, sizeof r) == -1)
+			die("write");
 		if(sleepms)
 			sleep(sleepms);
 	}
@@ -140,7 +143,7 @@
 	ratemb = i/delta/1024/1024;
 	if(sleepms > 0){
 		maxr = Blen*1000. / sleepms / 1e6;
-		print("%llud bytes in %g s @ %.2g MB/s (%ldms; limit %.2g MB/s)\n", i, delta, ratemb, sleepms, maxr);
+		print("%llud bytes in %g s @ %.2g MB/s (%dms; limit %.2g MB/s)\n", i, delta, ratemb, sleepms, maxr);
 	}
 	else
 		print("%llud bytes in %g s @ %.2g MB/s (0ms)\n", i, delta, ratemb);
@@ -165,6 +168,7 @@
 	case 'd':
 	case 'l':
 	case 't':
+	case 'p':
 		flag[ARGC()] = 1;
 		break;
 	case 'h':
@@ -186,7 +190,7 @@
 			sysfatal("%s: can't find my address", argv0);
 		switch(fork()){
 		case -1:
-			die();
+			die("fork");
 			break;
 		case 0:
 			server();
--- /sys/man/8/nettest	Sun May 10 18:24:55 2015
+++ /sys/man/8/nettest	Sun May 10 18:24:56 2015
@@ -5,6 +5,9 @@
 .B nettest
 .B -l
 [
+.B -dp
+]
+[
 .B -t
 [
 .B -e
@@ -103,6 +106,8 @@
 .PP
 In all modes, TLS may be pushed onto the network file descriptor.
 The options are
+.TF "-s sleepms"
+.PD 0
 .TP
 .B -t
 Enable TLS.
@@ -112,6 +117,18 @@
 .TP
 .B "-e \fIencalg\fP"
 Set the encryption algorithm.  The default is clear.
+.PP
+In all modes, RPC-mode or debugging printing can be enabled.
+The options are
+.TF "-s sleepms"
+.PD 0
+.TP
+.B -d
+print debugging information
+.TP
+.B -p
+ping-pong.  Emulate RPC by sending or expecting
+64-byte responses.
 .SH EXAMPLE
 To test a reader limited to 8MB/s
 .IP