Re: [lwip-users] udp checksum error

[Jonathan Larmour]

Muhamad Ikhwan Ismail wrote:
> I am using the socket API sending some dummy
> packets to a UDP echo server I setup on the other node. The sending went
> well except for I am having UDP checksum error.

See comments below.

> void test_udp_socket(void){
>     int socket_index;
>    
>     SCB_PTR suspend_udp;    //semaphore used to suspend the thread
>     suspend_udp = create_sema(1);
>    
>     socket_index = lwip_socket(AF_INET,SOCK_DGRAM,0x00);
>    
>     /*now get a sockaddr structure corresponding to socket domain AF_INET */
>     struct sockaddr_in* endpoint = (struct
> sockaddr_in*)mallocx(sizeof(struct sockaddr));   

At this point you should probably memset the contents of sockaddr_in to 0
(unless your mallocx does .

>     (endpoint)->sin_family = AF_INET;
>     (endpoint)->sin_port = (htons(7));
>     struct ip_addr server_ip;
>     IP4_ADDR(&server_ip,169,254,36,145);
>     (endpoint)->sin_addr.s_addr = server_ip.addr;
>     int addrlen = (endpoint)->sin_len = sizeof((endpoint)->sin_addr.s_addr);

The above line is wrong. You need addrlen to be sizeof(endpoint).

NB, there's no need to set sin_len - it exists only for compatibility with
other stacks, and isn't even part of the POSIX standard any more.

Jifl
-- 
eCosCentric Limited      http://www.eCosCentric.com/     The eCos experts
Barnwell House, Barnwell Drive, Cambridge, UK.       Tel: +44 1223 245571
Registered in England and Wales: Reg No 4422071.
------["Si fractum non sit, noli id reficere"]------       Opinions==mine