[lwip-devel] [bug #56355] PBUF_POOL_BUFSIZE avoid using multiple buffers for IPv6

[Tymoteusz Bloch]

URL:
  <https://savannah.nongnu.org/bugs/?56355>

                 Summary: PBUF_POOL_BUFSIZE  avoid using multiple buffers for
IPv6
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: tbloch
            Submitted on: Mon 20 May 2019 03:40:45 PM UTC
                Category: pbufs
                Severity: 3 - Normal
              Item Group: Change Request
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
            lwIP version: 2.1.1

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Details:

There were some problems with Mbed-OS using LWIP code and IPv6. 

Root cause was related pbuf's size. 

It's desirable to avoid using multiple buffers increase LWIP
PBUF_POOL_BUFSIZE. 

This involves selecting the default size by IP type.
IPv4 header needs 20 bytes more required by IPv6 header.

Proposed changes in opt.h

Replace:

#if !defined PBUF_POOL_BUFSIZE || defined __DOXYGEN__
#define PBUF_POOL_BUFSIZE               LWIP_MEM_ALIGN_SIZE(TCP_MSS+40+PB
UF_LINK_ENCAPSULATION_HLEN+PBUF_LINK_HLEN)
#endif

with:

#if !defined PBUF_POOL_BUFSIZE || defined __DOXYGEN__
#if LWIP_IPV6
#define PBUF_POOL_BUFSIZE              
LWIP_MEM_ALIGN_SIZE(TCP_MSS+20+40+PBUF_LINK_ENCAPSULATION_HLEN+PBUF_LINK_HLEN)
#elif LWIP_IPV4
#define PBUF_POOL_BUFSIZE              
LWIP_MEM_ALIGN_SIZE(TCP_MSS+20+20+PBUF_LINK_ENCAPSULATION_HLEN+PBUF_LINK_HLEN)
#endif
#endif




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