write() method for sockets in kernel

[zvoice]

Iperf client calls write() to send a message to iperf server. My aim - is to find out the way the information goes thru the kernel. First of all, i wanna find write method for sockets. it's something like that

int             (*sendmsg)   (struct kiocb *iocb, struct socket *sock,
                                      struct msghdr *m, size_t total_len);

Could u please help me?

[vthanki]

well, write() is the system call, which takes fd (ie. file descriptor) as one of the arguments. you can get the code of write() system call in <kernel_source_dir>/fs/open.c (i guess) and the function name would be sys_write().. now depending upon the file descriptor, kernel will identify that its a regular file descriptor or a socket descriptor. once it finds that the descriptor is socket, it will call the socket's write method, which will be pointing to "sendmsg".. i hope this helps..

[zvoice]

Thank you for your answer)))
I'll try to find socket's sendmsg method that way

[zvoice]

well, write() is the system call, which takes fd (ie. file descriptor) as one of the arguments. you can get the code of write() system call in <kernel_source_dir>/fs/open.c (i guess) and the function name would be sys_write().. now depending upon the file descriptor, kernel will identify that its a regular file descriptor or a socket descriptor. once it finds that the descriptor is socket, it will call the socket's write method, which will be pointing to "sendmsg".. i hope this helps..

there is no method like write() in open.c

[vthanki]

sorry about that.. u'll find it in fs/read_write.c (as u mentioned).. method name would be sys_write() (sys_<name>) is the convention for syscalls in linux..