patchlwIP - A Lightweight TCP/IP stack - Patches: patch #6410, Correlation between TCP MSS and...


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patch #6410: Correlation between TCP MSS and netif MTU

Submitted by:  Marc Chaland <chaland>
Submitted on:  Thu 07 Feb 2008 01:35:41 PM UTC  
Category:  None Priority:  5 - Normal
Status:  Works For Me Privacy:  Public
Assigned to:  Jonathan Larmour <jifl> Open/Closed:  Closed
Planned Release:  None

Tue 04 Mar 2008 03:38:35 PM UTC, comment #5: 

Yes. Looks like we can indeed close it.

Jonathan Larmour <jifl>
Project MemberIn charge of this item.
Tue 04 Mar 2008 01:16:28 PM UTC, comment #4: 

Just to clarify the status of this: as I understand the other comments TCP_CALCULATE_EFF_SEND_MSS does what was requested, and any remaining issues are covered by BUG22249.  Is that correct?  If so we can close this

Kieran Mansley <kieranm>
Project Member
Sun 10 Feb 2008 11:58:02 AM UTC, comment #3: 

Yes, that's it. Thank you for information. Just a remark linked with bug #22249 : MSS should be limited to a minimal size.


Marc Chaland <chaland>
Fri 08 Feb 2008 04:07:03 PM UTC, comment #2: 

Marc, have you enabled TCP_CALCULATE_EFF_SEND_MSS in lwipopts.h? It seems this does what you want.

It seems that comment #1 is unrelated, is that right?


Jonathan Larmour <jifl>
Project MemberIn charge of this item.
Thu 07 Feb 2008 01:39:13 PM UTC, comment #1: 

Sorry, I forgot :

into tcp_in.c line 80 (CVS-1.97) :
static err_t tcp_listen_input(struct tcp_pcb_listen *pcb, u16_t mtu);

into tcp_in.c line 242 (CVS-1.97) :
        tcp_listen_input(lpcb, inp->mtu);

into tcp_in.c line 393 (CVS-1.97) :
tcp_listen_input(struct tcp_pcb_listen *pcb, u16_t mtu)

Marc Chaland <chaland>
Thu 07 Feb 2008 01:35:41 PM UTC, original submission:  

When client tries to connect to lwip on one interface with a reduced MTU, MSS is not reduced.

I suggest following change :
into lwipopts.h, add the following define :
#define TCP_MSS_OFFSET          40

into tcp_in.c line 397 (CVS-1.97) :
  u16_t mss;
#endif /* TCP_MSS_OFFSET */

into tcp_in.c line 432 (CVS-1.97) :
    mss = mtu - TCP_MSS_OFFSET;
    if ((mss < npcb->mss) && (mss > TCP_MSS_MIN)) {
        npcb->mss = mss;
#endif /* TCP_MSS_OFFSET */

Marc Chaland <chaland>


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    Follow 3 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2008-03-04 jifl StatusNone => Works For Me
        Assigned toNone => jifl
        Open/ClosedOpen => Closed

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