For and exit so that inetd can have us be a "wait" service.

The problem with the old way is that there is a race between tftpd (starting
up) and inetd (after forking and execing) to see who gets to read from port
69 (the udp port).  If inetd wins, it will spawn another instance of tftpd.
So, we read the packet from port 69, then fork and the parent returns.

SCCS-vsn: libexec/tftpd/tftpd.c 5.6

diff --git a/usr/src/libexec/tftpd/tftpd.c b/usr/src/libexec/tftpd/tftpd.c
index 8a99725..9a9529e 100644 (file)
--- a/usr/src/libexec/tftpd/tftpd.c
+++ b/usr/src/libexec/tftpd/tftpd.c
@@ -11,7 +11,7 @@ char copyright[] =
 #endif not lint
 
 #ifndef lint
 #endif not lint
 
 #ifndef lint

-static char sccsid[] = "@(#)tftpd.c    5.5 (Berkeley) %G%";
+static char sccsid[] = "@(#)tftpd.c    5.6 (Berkeley) %G%";

 #endif not lint
 
 
 #endif not lint
 
 


@@ -57,31 +57,85 @@ main()
 {
        register struct tftphdr *tp;
        register int n;
 {
        register struct tftphdr *tp;
        register int n;

+       int on = 1;

 
        openlog("tftpd", LOG_PID, LOG_DAEMON);
 
        openlog("tftpd", LOG_PID, LOG_DAEMON);

-       alarm(10);
+       if (ioctl(0, FIONBIO, &on) < 0) {
+               syslog(LOG_ERR, "ioctl(FIONBIO): %m\n");
+               exit(1);
+       }

        fromlen = sizeof (from);
        n = recvfrom(0, buf, sizeof (buf), 0,
            (caddr_t)&from, &fromlen);
        if (n < 0) {
        fromlen = sizeof (from);
        n = recvfrom(0, buf, sizeof (buf), 0,
            (caddr_t)&from, &fromlen);
        if (n < 0) {

-               perror("tftpd: recvfrom");
+               syslog(LOG_ERR, "recvfrom: %m\n");

                exit(1);
        }
                exit(1);
        }

+       /*
+        * Now that we have read the message out of the UDP
+        * socket, we fork and exit.  Thus, inetd will go back
+        * to listening to the tftp port, and the next request
+        * to come in will start up a new instance of tftpd.
+        *
+        * We do this so that inetd can run tftpd in "wait" mode.
+        * The problem with tftpd running in "nowait" mode is that
+        * inetd may get one or more successful "selects" on the
+        * tftp port before we do our receive, so more than one
+        * instance of tftpd may be started up.  Worse, if tftpd
+        * break before doing the above "recvfrom", inetd would
+        * spawn endless instances, clogging the system.
+        */
+       {
+               int pid;
+               int i, j;
+
+               for (i = 1; i < 20; i++) {
+                   pid = fork();
+                   if (pid < 0) {
+                               sleep(i);
+                               /*
+                                * flush out to most recently sent request.
+                                *
+                                * This may drop some request, but those
+                                * will be resent by the clients when
+                                * they timeout.  The positive effect of
+                                * this flush is to (try to) prevent more
+                                * than one tftpd being started up to service
+                                * a single request from a single client.
+                                */
+                               j = sizeof from;
+                               i = recvfrom(0, buf, sizeof (buf), 0,
+                                   (caddr_t)&from, &j);
+                               if (i > 0) {
+                                       n = i;
+                                       fromlen = j;
+                               }
+                   } else {
+                               break;
+                   }
+               }
+               if (pid < 0) {
+                       syslog(LOG_ERR, "fork: %m\n");
+                       exit(1);
+               } else if (pid != 0) {
+                       exit(0);
+               }
+       }

        from.sin_family = AF_INET;
        alarm(0);
        close(0);
        close(1);
        peer = socket(AF_INET, SOCK_DGRAM, 0);
        if (peer < 0) {
        from.sin_family = AF_INET;
        alarm(0);
        close(0);
        close(1);
        peer = socket(AF_INET, SOCK_DGRAM, 0);
        if (peer < 0) {

-               syslog(LOG_ERR, "socket: %m");
+               syslog(LOG_ERR, "socket: %m\n");

                exit(1);
        }
        if (bind(peer, (caddr_t)&sin, sizeof (sin)) < 0) {
                exit(1);
        }
        if (bind(peer, (caddr_t)&sin, sizeof (sin)) < 0) {

-               syslog(LOG_ERR, "bind: %m");
+               syslog(LOG_ERR, "bind: %m\n");

                exit(1);
        }
        if (connect(peer, (caddr_t)&from, sizeof(from)) < 0) {
                exit(1);
        }
        if (connect(peer, (caddr_t)&from, sizeof(from)) < 0) {

-               syslog(LOG_ERR, "connect: %m");
+               syslog(LOG_ERR, "connect: %m\n");

                exit(1);
        }
        tp = (struct tftphdr *)buf;
                exit(1);
        }
        tp = (struct tftphdr *)buf;


@@ -236,7 +290,7 @@ sendfile(pf)
 
 send_data:
                if (send(peer, dp, size + 4, 0) != size + 4) {
 
 send_data:
                if (send(peer, dp, size + 4, 0) != size + 4) {

-                       perror("tftpd: write");
+                       syslog(LOG_ERR, "tftpd: write: %m\n");

                        goto abort;
                }
                read_ahead(file, pf->f_convert);
                        goto abort;
                }
                read_ahead(file, pf->f_convert);


@@ -245,7 +299,7 @@ send_data:
                        n = recv(peer, ackbuf, sizeof (ackbuf), 0);
                        alarm(0);
                        if (n < 0) {
                        n = recv(peer, ackbuf, sizeof (ackbuf), 0);
                        alarm(0);
                        if (n < 0) {

-                               perror("tftpd: read");
+                               syslog(LOG_ERR, "tftpd: read: %m\n");

                                goto abort;
                        }
                        ap->th_opcode = ntohs((u_short)ap->th_opcode);
                                goto abort;
                        }
                        ap->th_opcode = ntohs((u_short)ap->th_opcode);


@@ -299,7 +353,7 @@ recvfile(pf)
                (void) setjmp(timeoutbuf);
 send_ack:
                if (send(peer, ackbuf, 4, 0) != 4) {
                (void) setjmp(timeoutbuf);
 send_ack:
                if (send(peer, ackbuf, 4, 0) != 4) {

-                       perror("tftpd: write");
+                       syslog(LOG_ERR, "tftpd: write: %m\n");

                        goto abort;
                }
                write_behind(file, pf->f_convert);
                        goto abort;
                }
                write_behind(file, pf->f_convert);


@@ -308,7 +362,7 @@ send_ack:
                        n = recv(peer, dp, PKTSIZE, 0);
                        alarm(0);
                        if (n < 0) {            /* really? */
                        n = recv(peer, dp, PKTSIZE, 0);
                        alarm(0);
                        if (n < 0) {            /* really? */

-                               perror("tftpd: read");
+                               syslog(LOG_ERR, "tftpd: read: %m\n");

                                goto abort;
                        }
                        dp->th_opcode = ntohs((u_short)dp->th_opcode);
                                goto abort;
                        }
                        dp->th_opcode = ntohs((u_short)dp->th_opcode);


@@ -397,5 +451,5 @@ nak(error)
        tp->th_msg[length] = '\0';
        length += 5;
        if (send(peer, buf, length, 0) != length)
        tp->th_msg[length] = '\0';
        length += 5;
        if (send(peer, buf, length, 0) != length)

-               perror("nak");
+               syslog(LOG_ERR, "nak: %m\n");

 }
 }