[lwip-users] PBUF_POOL_BUFSIZE and Lwip Data Reception problem

[Lee Trueman]

Can anyone explain why when i have PBUF_POOL_BUFSIZE set to 128 i cannot transmitte a packet from PC to lwip that is over 128bytes in total (74bytes data + 54 Header etc).........

 

If I change the PBUF_POOL_BUFSIZE to 512, yes you have guessed it i can now only send 458bytes of data + 54 header and stuff = 512.......

 

What is going on here............ Here are my current lwip options........

 

* ---------- Pbuf options ---------- */

/* PBUF_POOL_SIZE: the number of buffers in the pbuf pool. */

#define PBUF_POOL_SIZE 16//32//10//8

/* PBUF_POOL_BUFSIZE: the size of each pbuf in the pbuf pool. */

#define PBUF_POOL_BUFSIZE 512//128//512//128//1100//128

/* PBUF_LINK_HLEN: the number of bytes that should be allocated for a

link level header. */

#define PBUF_LINK_HLEN 16

 

/* ---------- TCP options ---------- */

#define LWIP_TCP 1

#define TCP_TTL 255

/* Controls if TCP should queue segments that arrive out of

order. Define to 0 if your device is low on memory. */

#define TCP_QUEUE_OOSEQ 0//1

/* TCP Maximum segment size. */

#define TCP_MSS 1024//128//512//128//512//256//128

/* TCP sender buffer space (bytes). */

#define TCP_SND_BUF 4096//2048//1024//512//256

/* TCP sender buffer space (pbufs). This must be at least = 2 *

TCP_SND_BUF/TCP_MSS for things to work. */

#define TCP_SND_QUEUELEN 4 * TCP_SND_BUF/TCP_MSS//2 * TCP_SND_BUF/TCP_MSS//4 * TCP_SND_BUF/TCP_MSS

/* TCP receive window. */

#define TCP_WND 32768//1024//512//1100//1024

/* Maximum number of retransmissions of data segments. */

#define TCP_MAXRTX 12//1//12

/* Maximum number of retransmissions of SYN segments. */

#define TCP_SYNMAXRTX 4//1//4

/* TCP writable space (bytes). This must be less than or equal

to TCP_SND_BUF. It is the amount of space which must be

available in the tcp snd_buf for select to return writable */

#define TCP_SNDLOWAT TCP_SND_BUF/2

Regards

Lee