多进程并发编程----进程间传递文件描述符案例

#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<string.h>
#include<assert.h>
#include<errno.h>
#include<fcntl.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<sys/socket.h>

int send_fd(int fd, void *ptr, size_t nbytes, int sendfd)
{
struct msghdr	msg;
struct iovec	iov[1];
union {
struct cmsghdr	cm;
char	 control[CMSG_SPACE(sizeof(int))];
} control_un;
struct cmsghdr	*cmptr;
msg.msg_control = control_un.control;
msg.msg_controllen = sizeof(control_un.control);

cmptr = CMSG_FIRSTHDR(&msg);
cmptr->cmsg_len = CMSG_LEN(sizeof(int));
cmptr->cmsg_level = SOL_SOCKET;
cmptr->cmsg_type = SCM_RIGHTS;
*((int *) CMSG_DATA(cmptr)) = sendfd;

msg.msg_name = NULL;
msg.msg_namelen = 0;

iov[0].iov_base = ptr;
iov[0].iov_len = nbytes;
msg.msg_iov = iov;
msg.msg_iovlen = 1;

return(sendmsg(fd, &msg, 0));
}
int recv_fd(int sockfd,void *data,size_t size,int *fd){
int num;
struct msghdr msg;
struct cmsghdr *cmsgptr;
struct iovec vec[1];
union{
struct cmsghdr cmsg;
char   control[CMSG_SPACE(sizeof(int))];
}control_un;

msg.msg_control = control_un.control;
msg.msg_controllen = sizeof(control_un.control);

vec[0].iov_base=data;
vec[0].iov_len=size;

msg.msg_name=NULL;
msg.msg_namelen=0;
msg.msg_iov=vec;
msg.msg_iovlen=1;

if((num=recvmsg(sockfd,&msg,0))==-1){
printf("recvmsg error:%s\n",strerror(errno));
return num;
}

if((cmsgptr=CMSG_FIRSTHDR(&msg))!= NULL && cmsgptr->cmsg_len==CMSG_LEN(sizeof(int))){
if(cmsgptr->cmsg_level != SOL_SOCKET)
printf("control level != SOL_SOCKET\n");
if(cmsgptr->cmsg_type != SCM_RIGHTS)
printf("control type != SCM_RIGHTS\n");
*fd=*((int *)CMSG_DATA(cmsgptr));
}
else
*fd = -1;		/* descriptor was not passed */

return num;
}

int main(){
char filebuf[1024];
char sendbuf[256];
char recvbuf[256];
int sockfd[2];
int pid;
int fd;
int ret,state,num;
ret=socketpair(AF_UNIX,SOCK_STREAM,0,sockfd);
assert(ret!=-1);
pid=fork();
if(pid==0){
close(sockfd[0]);
fd=open("wordexp.c",O_RDONLY,0666);
assert(fd!=-1);
memset(sendbuf,0,sizeof(sendbuf));
sprintf(sendbuf,"%s","hello,mm");
num=send_fd(sockfd[1],sendbuf,sizeof(sendbuf),fd);
close(fd);
exit(5);
}
waitpid(pid,&state,0);
if(WIFEXITED(state)){
printf("child is exited,state[%d]\n",WEXITSTATUS(state));
close(sockfd[1]);
memset(recvbuf,0,sizeof(recvbuf));
num=recv_fd(sockfd[0],recvbuf,sizeof(recvbuf),&fd);
printf("recvbuf:[%s]\n",recvbuf);
memset(filebuf,0,sizeof(filebuf));
read(fd,filebuf,sizeof(filebuf));
printf("buf:[%s]\n",filebuf);
close(fd);
}

return 0;
}