tftpd: implement the "rollover" option

Implement the "rollover" option, to set the rollover block number to
anything other than zero.  Apparently some idiots have gotten the idea
that block numbers should roll over to one, rather than zero.

2 files changed, 28 insertions, 2 deletions

diff --git a/tftpd/tftpd.8.in b/tftpd/tftpd.8.in
index a469ac8..f42d874 100644
--- a/tftpd/tftpd.8.in
+++ b/tftpd/tftpd.8.in
@@ -218,6 +218,10 @@ Set the time before the server retransmits a packet, in seconds.
 .TP
 \fButimeout\fP (nonstandard)
 Set the time before the server retransmits a packet, in microseconds.
+.TP
+\fBrollover\fP (nonstandard)
+Set the block number to resume at after a block number rollover.  The
+default and recommended value is zero.
 .PP
 The
 .B \-\-refuse
diff --git a/tftpd/tftpd.c b/tftpd/tftpd.c
index 3c96844..f98d52b 100644
--- a/tftpd/tftpd.c
+++ b/tftpd/tftpd.c
@@ -81,6 +81,7 @@ static unsigned long rexmtval = TIMEOUT;       /* Basic timeout value */
 static unsigned long maxtimeout = TIMEOUT_LIMIT * TIMEOUT;
 static int timeout_quit = 0;
 static sigjmp_buf timeoutbuf;
+static uint16_t rollover_val = 0;
 
 #define	PKTSIZE	MAX_SEGSIZE+4
 static char buf[PKTSIZE];
@@ -119,6 +120,7 @@ static int set_blksize2(char *, char **);
 static int set_tsize(char *, char **);
 static int set_timeout(char *, char **);
 static int set_utimeout(char *, char **);
+static int set_rollover(char *, char **);
 
 struct options {
     const char *o_opt;
@@ -129,6 +131,7 @@ struct options {
     {"tsize",    set_tsize},
     {"timeout",  set_timeout},
     {"utimeout", set_utimeout},
+    {"rollover", set_rollover},
     {NULL, NULL}
 };
 
@@ -1161,6 +1164,23 @@ static int set_blksize2(char *val, char **ret)
 }
 
 /*
+ * Set the block number rollover value
+ */
+static int set_rollover(char *val, char **ret)
+{
+  uintmax_t ro;
+  char *vend;
+
+  ro = strtoumax(val, &vend, 10);
+  if (ro > 65535 || *vend)
+    return 0;
+
+  rollover_val = (uint16_t)ro;
+  *ret = val;
+  return 1;
+}
+
+/*
  * Return a file size (c.f. RFC2349)
  * For netascii mode, we don't know the size ahead of time;
  * so reject the option.
@@ -1542,7 +1562,8 @@ static void tftp_sendfile(struct formats *pf, struct tftphdr *oap, int oacklen)
             }
 
         }
-        block++;
+	if (!++block)
+	  block = rollover_val;
     } while (size == segsize);
   abort:
     (void)fclose(file);
@@ -1575,7 +1596,8 @@ static void tftp_recvfile(struct formats *pf, struct tftphdr *oap, int oacklen)
             ap->th_block = htons((u_short) block);
             acksize = 4;
         }
-        block++;
+        if (!++block)
+	  block = rollover_val;
         (void)sigsetjmp(timeoutbuf, 1);
       send_ack:
         r_timeout = timeout;