原來我們實作connect()逾時基本上都使用unix網絡程式設計一書的非阻塞方式(connect_nonb),今天在網上看到一篇文章,覺得很有意思,轉載如下:
讀Linux核心源碼的時候偶然發現其connect的逾時參數竟然和用SO_SNDTIMO操作的參數一緻:
File: net/ipv4/af_inet.c
559 timeo = sock_sndtimeo(sk, flags & O_NONBLOCK); 560 561 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { 562 563 if (!timeo || !inet_wait_for_connect(sk, timeo)) 564 goto out; 565 566 err = sock_intr_errno(timeo); 567 if (signal_pending(current)) 568 goto out; 569 } |
這意味着: 在Linux平台下,可以通過在connect之前設定SO_SNDTIMO來達到控制連接配接逾時的目的。簡單的寫了份測試代碼:
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <errno.h>
int main(int argc, char *argv[])
{
int fd;
struct sockaddr_in addr;
struct timeval timeo = {3, 0};
socklen_t len = sizeof(timeo);
fd = socket(AF_INET, SOCK_STREAM, 0);
if (argc == 4)
timeo.tv_sec = atoi(argv[3]);
setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, &timeo, len);
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = inet_addr(argv[1]);
addr.sin_port = htons(atoi(argv[2]));
if (connect(fd, (struct sockaddr*)&addr, sizeof(addr)) == -1) {
if (errno == EINPROGRESS) {
fprintf(stderr, "timeout/n");
return -1;
}
perror("connect");
return 0;
}
printf("connected/n");
return 0;
} |
附一篇文章:【SO_SNDTIMEO對connect的影響】http://blog.aka-cool.net/blog/2014/11/20/so-sndtimeo-have-effects-on-connect/