[lwip-devel] [bug #18782] the default PBUF_POOL_BUFSIZE value should be changed

[dupengbo]

URL:
  <http://savannah.nongnu.org/bugs/?18782>

                 Summary: the default PBUF_POOL_BUFSIZE value should be
changed
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: dupengbo
            Submitted on: Monday 01/15/07 at 03:37
                Category: IPv4
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any

    _______________________________________________________

Details:

for example:
A is LWIP system , B is other TCPIP system.

A: the default TCP_WND is 2048, PBUF_POOL_SIZE is 16, PBUF_POOL_BUFSIZE  is
128. TCP_MSS is 128.
static u8_t pbuf_pool_memory[MEM_ALIGNMENT - 1 + PBUF_POOL_SIZE *
MEM_ALIGN_SIZE(PBUF_POOL_BUFSIZE + sizeof(struct pbuf))];
the size of pbuf_pool_memory is 2048.

B: has known A has 2048 bytes available buffer.

So, B will send 2048 bytes to A (do not wait the ACK from A).

But B will send 128 + TCP header + IP header = 168 bytes to A.
LWIP will need two POOLs to save the data, because the PBUF_POOL_BUFSIZE  is
128, it could not save the 168 bytes data.

the result: B know the A has 2048 bytes available buffer, but actually A only
has 1024 bytes buffer available, because every segment need two POOLs.

suggestion: PBUF_POOL_BUFSIZE is 128 + TCP header + IP header






    _______________________________________________________

Reply to this item at:

  <http://savannah.nongnu.org/bugs/?18782>

_______________________________________________
  Message sent via/by Savannah
  http://savannah.nongnu.org/