Add DTLS support to NSS, contributed by Eric Rescorla.

net/third_party/nss/ssl/sslsecur.c

 /*
  * Various SSL functions.
  *
  * ***** BEGIN LICENSE BLOCK *****
  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
  *
  * The contents of this file are subject to the Mozilla Public License Version
  * 1.1 (the "License"); you may not use this file except in compliance with
  * the License. You may obtain a copy of the License at
  * http://www.mozilla.org/MPL/
@@ skipping 101 matching lines @@
 ssl_Do1stHandshake(sslSocket *ss)
 {
     int rv        = SECSuccess;
     int loopCount = 0;
 
     do {
         PORT_Assert(ss->opt.noLocks ||  ssl_Have1stHandshakeLock(ss) );
         PORT_Assert(ss->opt.noLocks || !ssl_HaveRecvBufLock(ss));
         PORT_Assert(ss->opt.noLocks || !ssl_HaveXmitBufLock(ss));
         PORT_Assert(ss->opt.noLocks || !ssl_HaveSSL3HandshakeLock(ss));
-
+        
         if (ss->handshake == 0) {
             /* Previous handshake finished. Switch to next one */
             ss->handshake = ss->nextHandshake;
             ss->nextHandshake = 0;
         }
         if (ss->handshake == 0) {
             /* Previous handshake finished. Switch to security handshake */
             ss->handshake = ss->securityHandshake;
             ss->securityHandshake = 0;
         }
@@ skipping 423 matching lines @@
 {
     int              rv;
     int              amount;
     int              available;
 
     ssl_GetRecvBufLock(ss);
 
     available = ss->gs.writeOffset - ss->gs.readOffset;
     if (available == 0) {
         /* Get some more data */
-        if (ss->version >= SSL_LIBRARY_VERSION_3_0) {
+        if (ss->version >= SSL_LIBRARY_VERSION_3_0) {
             /* Wait for application data to arrive.  */
             rv = ssl3_GatherAppDataRecord(ss, 0);
         } else {
             /* See if we have a complete record */
             rv = ssl2_GatherRecord(ss, 0);
         }
         if (rv <= 0) {
             if (rv == 0) {
                 /* EOF */
                 SSL_TRC(10, ("%d: SSL[%d]: ssl_recv EOF",
@@ skipping 31 matching lines @@
         SSL_TRC(30, ("%d: SSL[%d]: partial data ready, available=%d",
                      SSL_GETPID(), ss->fd, available));
     }
 
     /* Dole out clear data to reader */
     amount = PR_MIN(len, available);
     PORT_Memcpy(out, ss->gs.buf.buf + ss->gs.readOffset, amount);
     if (!(flags & PR_MSG_PEEK)) {
         ss->gs.readOffset += amount;
     }
+    PORT_Assert(ss->gs.readOffset <= ss->gs.writeOffset);

[wtc, 2012/03/21 01:22:07]

Did you mean to add this assertion, or did you add it for
debugging and forget to remove it?

[ekr, 2012/03/21 01:36:40]

I suspect that I added it for debugging and forgot to remove it, but OTOH, it
seems like in fact it should be an invariant, right?

[wtc, 2012/03/21 02:12:01]

I am not familiar with this code, but I suspect this should
be an invariant because the code above does
    available = ss->gs.writeOffset - ss->gs.readOffset;
in two places and appears to assume available is >= 0.

Is this the best place to check this invariant?

     rv = amount;
 
     SSL_TRC(30, ("%d: SSL[%d]: amount=%d available=%d",
                  SSL_GETPID(), ss->fd, amount, available));
     PRINT_BUF(4, (ss, "DoRecv receiving plaintext:", out, amount));
 
 done:
     ssl_ReleaseRecvBufLock(ss);
     return rv;
 }
@@ skipping 957 matching lines @@
     if (!ss) {
         SSL_DBG(("%d: SSL[%d]: bad socket in SNISocketConfigHook",
                  SSL_GETPID(), fd));
         return SECFailure;
     }
 
     ss->sniSocketConfig = func;
     ss->sniSocketConfigArg = arg;
     return SECSuccess;
 }