accept.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

/* posix */
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>

/* bsd extensions */
#include <sys/uio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/un.h>

#include "priv.h"

int
accept(int fd, void *a, int *alen)
{
	int n, nfd, cfd;
	Rock *r, *nr;
	struct sockaddr_in *ip;
	char name[Ctlsize];
	char file[Ctlsize];
	char *p, *net;

	r = _sock_findrock(fd, 0);
	if(r == 0){
		errno = ENOTSOCK;
		return -1;
	}

	switch(r->domain){
	case PF_INET:
		switch(r->stype){
		case SOCK_DGRAM:
			net = "udp";
			break;
		case SOCK_STREAM:
			net = "tcp";
			break;
		}

		/* get control file name from listener process */
		n = read(fd, name, sizeof(name)-1);
		if(n <= 0){
			_syserrno();
			return -1;
		}
		name[n] = 0;
		cfd = open(name, O_RDWR);
		if(cfd < 0){
			_syserrno();
			return -1;
		}

		nfd = _sock_data(cfd, net, r->domain, r->stype, r->protocol, &nr);
		if(nfd < 0){
			_syserrno();
			return -1;
		}

		if(write(fd, "OK", 2) < 0){
			close(nfd);
			_syserrno();
			return -1;
		}

		/* get remote address */
		ip = (struct sockaddr_in*)&nr->raddr;
		_sock_ingetaddr(nr, ip, &n, "remote");
		if(a){
			memmove(a, ip, sizeof(struct sockaddr_in));
			*alen = sizeof(struct sockaddr_in);
		}

		return nfd;
	case PF_UNIX:
		if(r->other >= 0){
			errno = EGREG;
			return -1;
		}

		for(;;){
			/* read path to new connection */
			n = read(fd, name, sizeof(name) - 1);
			if(n < 0)
				return -1;
			if(n == 0)
				continue;
			name[n] = 0;

			/* open new connection */
			_sock_srvname(file, name);
			nfd = open(file, O_RDWR);
			if(nfd < 0)
				continue;

			/* confirm opening on new connection */
			if(write(nfd, name, strlen(name)) > 0)
				break;

			close(nfd);
		}

		nr = _sock_newrock(nfd);
		if(nr == 0){
			close(nfd);
			return -1;
		}
		nr->domain = r->domain;
		nr->stype = r->stype;
		nr->protocol = r->protocol;

		return nfd;
	default:
		errno = EOPNOTSUPP;
		return -1;
	}
}