LWIP problem, cannot send frame smaller than 952Bytes

Hi,

 

I'm using LWIP stack with a virtex5 PPC440 and HDMA(8192 buffers of 2048 Bytes).

It's actually working pretty well (250Mbps), with frame between 952Bytes to 64KBytes.

 

My problem is that when i use the tcp_write() function, i have to put frame lenght with a multiple of 2048 bigger than 952Bytes (average).

For example :

2040 Bytes => OK

556 Bytes => BAD

4088 Bytes => 2048 + 2040 => OK

4120 Bytes => 2048 + 2048 + 24 => BAD

 

It's really strange and i don't understand at all why i cannot put the size i want. Anyway when i'm on a bad way i get a tcp_err = -4 that correspond to "#define ERR_ABRT       -4    /* Connection aborted.      */"

 

Can someone help me please !!!

Thank you so much

 

bellow my lwipopts.h:

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#ifndef __LWIPOPTS_H_
#define __LWIPOPTS_H_

#define SYS_LIGHTWEIGHT_PROT 1

#define NO_SYS 1
#define LWIP_SOCKET 0
#define LWIP_COMPAT_SOCKETS 0
#define LWIP_NETCONN 0

#define MEM_ALIGNMENT 64
#define MEM_SIZE 131072
#define MEMP_NUM_PBUF 16
#define MEMP_NUM_UDP_PCB 4
#define MEMP_NUM_TCP_PCB 32
#define MEMP_NUM_TCP_PCB_LISTEN 8
#define MEMP_NUM_TCP_SEG 256
#define LWIP_USE_HEAP_FROM_INTERRUPT 1

#define MEMP_NUM_SYS_TIMEOUT 8
#define PBUF_POOL_SIZE 256
#define PBUF_POOL_BUFSIZE 1700
#define PBUF_LINK_HLEN 16

#define ARP_TABLE_SIZE 10
#define ARP_QUEUEING 1

#define ICMP_TTL 255

#define IP_OPTIONS 0
#define IP_FORWARD 0
#define IP_REASSEMBLY 1
#define IP_FRAG 1
#define IP_REASS_BUFSIZE 5760
#define IP_FRAG_MAX_MTU 1500
#define IP_DEFAULT_TTL 255
#define LWIP_CHKSUM_ALGORITHM 3

#define LWIP_UDP 1
#define UDP_TTL 255

#define LWIP_TCP 1
#define TCP_SND_QUEUELEN   16 * TCP_SND_BUF/TCP_MSS
#define TCP_MSS 1460
#define TCP_SND_BUF 8192
#define TCP_WND 2048
#define TCP_TTL 255
#define TCP_MAXRTX 12
#define TCP_SYNMAXRTX 4
#define TCP_QUEUE_OOSEQ 1
#define CHECKSUM_GEN_TCP 0
#define CHECKSUM_CHECK_TCP 0

#define LWIP_DHCP 0
#define DHCP_DOES_ARP_CHECK false

#define CONFIG_LINKSPEED_AUTODETECT 1

#endif
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