Implement nc -W recvlimit to terminate netcat after receiving a

number of packets.  This allows to send a UDP request, receive a
reply and check the result on the command line.
input jmc@; OK millert@

2 files changed, 28 insertions, 8 deletions

diff --git a/src/usr.bin/nc/nc.1 b/src/usr.bin/nc/nc.1
index 1b753e3d80..b1fa272040 100644
--- a/src/usr.bin/nc/nc.1
+++ b/src/usr.bin/nc/nc.1
@@ -1,4 +1,4 @@
-.\"     $OpenBSD: nc.1,v 1.84 2017/04/05 06:55:59 jmc Exp $
+.\"     $OpenBSD: nc.1,v 1.85 2017/05/10 21:56:53 bluhm Exp $
 .\"
 .\" Copyright (c) 1996 David Sacerdote
 .\" All rights reserved.
@@ -25,7 +25,7 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: April 5 2017 $
+.Dd $Mdocdate: May 10 2017 $
 .Dt NC 1
 .Os
 .Sh NAME
@@ -50,6 +50,7 @@
 .Op Fl s Ar source
 .Op Fl T Ar keyword
 .Op Fl V Ar rtable
+.Op Fl W Ar recvlimit
 .Op Fl w Ar timeout
 .Op Fl X Ar proxy_protocol
 .Op Fl x Ar proxy_address Ns Op : Ns Ar port
@@ -288,6 +289,10 @@ Set the routing table to be used.
 Have
 .Nm
 give more verbose output.
+.It Fl W Ar recvlimit
+Terminate after receiving
+.Ar recvlimit
+packets from the network.
 .It Fl w Ar timeout
 Connections which cannot be established or are idle timeout after
 .Ar timeout
diff --git a/src/usr.bin/nc/netcat.c b/src/usr.bin/nc/netcat.c
index bd9fb09a0f..54ebacf9ea 100644
--- a/src/usr.bin/nc/netcat.c
+++ b/src/usr.bin/nc/netcat.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: netcat.c,v 1.181 2017/04/16 15:11:01 deraadt Exp $ */
+/* $OpenBSD: netcat.c,v 1.182 2017/05/10 21:56:53 bluhm Exp $ */
 /*
  * Copyright (c) 2001 Eric Jackson <ericj@monkey.org>
  * Copyright (c) 2015 Bob Beck.  All rights reserved.
@@ -108,6 +108,7 @@ char	*tls_expectname;			/* required name in peer cert */
 char    *tls_expecthash;                        /* required hash of peer cert */
 FILE    *Zflag;                                 /* file to save peer cert */
 
+int recvcount, recvlimit;
 int timeout = -1;
 int family = AF_UNSPEC;
 char *portlist[PORT_MAX+1];
@@ -167,7 +168,8 @@ main(int argc, char *argv[])
         signal(SIGPIPE, SIG_IGN);
 
         while ((ch = getopt(argc, argv,
-            "46C:cDde:FH:hI:i:K:klM:m:NnO:o:P:p:R:rSs:T:tUuV:vw:X:x:Z:z")) != -1) {
+            "46C:cDde:FH:hI:i:K:klM:m:NnO:o:P:p:R:rSs:T:tUuV:vW:w:X:x:Z:z"))
+            != -1) {
                 switch (ch) {
                 case '4':
                         family = AF_INET;
@@ -270,6 +272,11 @@ main(int argc, char *argv[])
                 case 'v':
                         vflag = 1;
                         break;
+                case 'W':
+                        recvlimit = strtonum(optarg, 1, INT_MAX, &errstr);
+                        if (errstr)
+                                errx(1, "receive limit %s: %s", errstr, optarg);
+                        break;
                 case 'w':
                         timeout = strtonum(optarg, 0, INT_MAX / 1000, &errstr);
                         if (errstr)
@@ -1166,6 +1173,12 @@ readwrite(int net_fd, struct tls *tls_ctx)
                                 shutdown(pfd[POLL_NETIN].fd, SHUT_RD);
                                 pfd[POLL_NETIN].fd = -1;
                         }
+                        if (recvlimit > 0 && ++recvcount >= recvlimit) {
+                                if (pfd[POLL_NETIN].fd != -1)
+                                        shutdown(pfd[POLL_NETIN].fd, SHUT_RD);
+                                pfd[POLL_NETIN].fd = -1;
+                                pfd[POLL_STDIN].fd = -1;
+                        }
                         /* read something - poll stdout */
                         if (netinbufpos > 0)
                                 pfd[POLL_STDOUT].events = POLLOUT;
@@ -1706,6 +1719,7 @@ help(void)
         \t-u            UDP mode\n\
         \t-V rtable     Specify alternate routing table\n\
         \t-v            Verbose\n\
+        \t-W recvlimit  Terminate after receiving a number of packets\n\
         \t-w timeout    Timeout for connects and final net reads\n\
         \t-X proto      Proxy protocol: \"4\", \"5\" (SOCKS) or \"connect\"\n\
         \t-x addr[:port]\tSpecify proxy address and port\n\
@@ -1724,10 +1738,11 @@ usage(int ret)
             "\t  [-i interval] [-K keyfile] [-M ttl] [-m minttl] [-O length]\n"
             "\t  [-o staplefile] [-P proxy_username] [-p source_port] "
             "[-R CAfile]\n"
-            "\t  [-s source] [-T keyword] [-V rtable] [-w timeout] "
-            "[-X proxy_protocol]\n"
-            "\t  [-x proxy_address[:port]] [-Z peercertfile] "
-            "[destination] [port]\n");
+            "\t  [-s source] [-T keyword] [-V rtable] [-W recvlimit] "
+            "[-w timeout]\n"
+            "\t  [-X proxy_protocol] [-x proxy_address[:port]] "
+            "[-Z peercertfile]\n"
+            "\t  [destination] [port]\n");
         if (ret)
                 exit(1);
 }