[lwip-devel] [bug #22249] TCP MSS set to 0 into TCP option

[Marc Chaland]

URL:
  <http://savannah.nongnu.org/bugs/?22249>

                 Summary: TCP MSS set to 0 into TCP option
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: chaland
            Submitted on: jeudi 07.02.2008 à 13:26
                Category: TCP
                Severity: 3 - Normal
              Item Group: Crash Error
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: 

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Details:

If client tries to connect with a TCP MSS option set to 0, division by 0
exception occurs. Server side should limit minimum size for MSS to 536 into
tcp_parseopt() function.

I suggest following changes:

into lwipopts.h, add following define :
#define TCP_MSS_MIN             536
into tcp_in.c replace line 1334 (CVS-1.97) by :
        if ((mss < pcb->mss) && (mss > TCP_MSS_MIN)) {
            pcb->mss = mss;
        }
        if (mss < TCP_MSS_MIN) {
            pcb->mss = TCP_MSS_MIN;
        }

In fact, MSS should not be increased during one connection.




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