[Xen-changelog] [qemu-xen master] ui: track how much decoded data we consumed when doing SASL encoding

[patchbot@xxxxxxx]

commit 8a9c5c34ac978844eff539b711a7839e4d352958
Author:     Daniel P. Berrange <berrange@xxxxxxxxxx>
AuthorDate: Mon Dec 18 19:12:20 2017 +0000
Commit:     Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon Feb 12 18:33:50 2018 -0600

    ui: track how much decoded data we consumed when doing SASL encoding
    
    When we encode data for writing with SASL, we encode the entire pending 
output
    buffer. The subsequent write, however, may not be able to send the full 
encoded
    data in one go though, particularly with a slow network. So we delay 
setting the
    output buffer offset back to zero until all the SASL encoded data is sent.
    
    Between encoding the data and completing sending of the SASL encoded data,
    however, more data might have been placed on the pending output buffer. So 
it
    is not valid to set offset back to zero. Instead we must keep track of how 
much
    data we consumed during encoding and subtract only that amount.
    
    With the current bug we would be throwing away some pending data without 
having
    sent it at all. By sheer luck this did not previously cause any serious 
problem
    because appending data to the send buffer is always an atomic action, so we
    only ever throw away complete RFB protocol messages. In the case of frame 
buffer
    updates we'd catch up fairly quickly, so no obvious problem was visible.
    
    Signed-off-by: Daniel P. Berrange <berrange@xxxxxxxxxx>
    Reviewed-by: Darren Kenny <darren.kenny@xxxxxxxxxx>
    Reviewed-by: Marc-André Lureau <marcandre.lureau@xxxxxxxxxx>
    Message-id: 20171218191228.31018-6-berrange@xxxxxxxxxx
    Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
    (cherry picked from commit 8f61f1c5a6bc06438a1172efa80bc7606594fa07)
    Signed-off-by: Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
---
 ui/vnc-auth-sasl.c | 3 ++-
 ui/vnc-auth-sasl.h | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/ui/vnc-auth-sasl.c b/ui/vnc-auth-sasl.c
index 23f2828..761493b 100644
--- a/ui/vnc-auth-sasl.c
+++ b/ui/vnc-auth-sasl.c
@@ -67,6 +67,7 @@ long vnc_client_write_sasl(VncState *vs)
         if (err != SASL_OK)
             return vnc_client_io_error(vs, -1, NULL);
 
+        vs->sasl.encodedRawLength = vs->output.offset;
         vs->sasl.encodedOffset = 0;
     }
 
@@ -78,7 +79,7 @@ long vnc_client_write_sasl(VncState *vs)
 
     vs->sasl.encodedOffset += ret;
     if (vs->sasl.encodedOffset == vs->sasl.encodedLength) {
-        vs->output.offset = 0;
+        vs->output.offset -= vs->sasl.encodedRawLength;
         vs->sasl.encoded = NULL;
         vs->sasl.encodedOffset = vs->sasl.encodedLength = 0;
     }
diff --git a/ui/vnc-auth-sasl.h b/ui/vnc-auth-sasl.h
index cb42745..b9d8de1 100644
--- a/ui/vnc-auth-sasl.h
+++ b/ui/vnc-auth-sasl.h
@@ -53,6 +53,7 @@ struct VncStateSASL {
      */
     const uint8_t *encoded;
     unsigned int encodedLength;
+    unsigned int encodedRawLength;
     unsigned int encodedOffset;
     char *username;
     char *mechlist;
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#master

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