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  1. 11 Jun, 2008 5 commits
    • Gerrit Renker's avatar
      dccp ccid-3: X truncated due to type conversion · 7deb0f85
      Gerrit Renker authored 
      This fixes a bug in computing the inter-packet-interval t_ipi = s/X: 

 scaled_div32(a, b) uses u32 for b, but in "scaled_div32(s, X)" the type of the
 sending rate `X' is u64. Since X is scaled by 2^6, this truncates rates greater
 than 2^26 Bps (~537 Mbps).

Using full 64-bit division now.
Signed-off-by: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
      7deb0f85
    • Gerrit Renker's avatar
      dccp ccid-3: TFRC reverse-lookup Bug-Fix · 1e8a287c
      Gerrit Renker authored 
      This fixes a bug in the reverse lookup of p: given a value f(p), instead of p,
the function returned the smallest tabulated value f(p).

The smallest tabulated value of
	 
   10^6 * f(p) =  sqrt(2*p/3) + 12 * sqrt(3*p/8) * (32 * p^3 + p) 

for p=0.0001 is 8172. 

Since this value is scaled by 10^6, the outcome of this bug is that a loss
of 8172/10^6 = 0.8172% was reported whenever the input was below the table
resolution of 0.01%.

This means that the value was over 80 times too high, resulting in large spikes
of the initial loss interval, thus unnecessarily reducing the throughput.

Also corrected the printk format (%u for u32).
Signed-off-by: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
      1e8a287c
    • Gerrit Renker's avatar
      dccp ccid-2: Bug-Fix - Ack Vectors need to be ignored on request sockets · 65907a43
      Gerrit Renker authored 
      This fixes an oversight from an earlier patch, ensuring that Ack Vectors
are not processed on request sockets.

The issue is that Ack Vectors must not be parsed on request sockets, since
the Ack Vector feature depends on the selection of the (TX) CCID. During the
initial handshake the CCIDs are undefined, and so RFC 4340, 10.3 applies:

 "Using CCID-specific options and feature options during a negotiation
  for the corresponding CCID feature is NOT RECOMMENDED [...]"

And it is not even possible: when the server receives the Request from the 
client, the CCID and Ack vector features are undefined; when the Ack finalising
the 3-way hanshake arrives, the request socket has not been cloned yet into a
full socket. (This order is necessary, since otherwise the newly created socket
would have to be destroyed whenever an option error occurred - a malicious
hacker could simply send garbage options and exploit this.)
Signed-off-by: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
      65907a43
    • Gerrit Renker's avatar
      dccp: Fix sparse warnings · 1e2f0e5e
      Gerrit Renker authored 
      This patch fixes the following sparse warnings:
 * nested min(max()) expression:
   net/dccp/ccids/ccid3.c:91:21: warning: symbol '__x' shadows an earlier one
   net/dccp/ccids/ccid3.c:91:21: warning: symbol '__y' shadows an earlier one
   
 * Declaration of function prototypes in .c instead of .h file, resulting in
   "should it be static?" warnings. 

 * Declared "struct dccpw" static (local to dccp_probe).
 
 * Disabled dccp_delayed_ack() - not fully removed due to RFC 4340, 11.3
   ("Receivers SHOULD implement delayed acknowledgement timers ...").

 * Used a different local variable name to avoid
   net/dccp/ackvec.c:293:13: warning: symbol 'state' shadows an earlier one
   net/dccp/ackvec.c:238:33: originally declared here

 * Removed unused functions `dccp_ackvector_print' and `dccp_ackvec_print'.
Signed-off-by: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
      1e2f0e5e
    • Gerrit Renker's avatar
      dccp ccid-3: Bug-Fix - Zero RTT is possible · 3294f202
      Gerrit Renker authored 
      In commit $(825de27d) (from 27th May, commit
message `dccp ccid-3: Fix "t_ipi explosion" bug'), the CCID-3 window counter
computation was fixed to cope with RTTs < 4 microseconds.

Such RTTs can be found e.g. when running CCID-3 over loopback. The fix removed
a check against RTT < 4, but introduced a divide-by-zero bug.

All steady-state RTTs in DCCP are filtered using dccp_sample_rtt(), which
ensures non-zero samples. However, a zero RTT is possible on initialisation,
when there is no RTT sample from the Request/Response exchange.

The fix is to use the fallback-RTT from RFC 4340, 3.4.

This is also better than just fixing update_win_count() since it allows other
parts of the code to always assume that the RTT is non-zero during the time
that the CCID is used.
Signed-off-by: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
      3294f202
  3. 10 Jun, 2008 28 commits
  5. 09 Jun, 2008 7 commits