http://blog.csdn.net/ly21st http://ly21st.blog.chinaunix.net
分类： LINUX
2011-09-19 19:37:02
获取和设置影响套接口的选项：
1）函数getsockopt和setsockopt
2）函数fcntl
3）函数ioctl
7.3 检查选项是否受支持并获取缺省值/* include checkopts1 */
/* *INDENT-OFF* */
#include "unp.h"
#include
union val {
int i_val;
long l_val;
struct linger linger_val;
struct timeval timeval_val;
} val;
static char *sock_str_flag(union val *, int);
static char *sock_str_int(union val *, int);
static char *sock_str_linger(union val *, int);
static char *sock_str_timeval(union val *, int);
struct sock_opts {
const char *opt_str;
int opt_level;
int opt_name;
char *(*opt_val_str)(union val *, int);
} sock_opts[] = {
{ "SO_BROADCAST", SOL_SOCKET, SO_BROADCAST, sock_str_flag },
{ "SO_DEBUG", SOL_SOCKET, SO_DEBUG, sock_str_flag },
{ "SO_DONTROUTE", SOL_SOCKET, SO_DONTROUTE, sock_str_flag },
{ "SO_ERROR", SOL_SOCKET, SO_ERROR, sock_str_int },
{ "SO_KEEPALIVE", SOL_SOCKET, SO_KEEPALIVE, sock_str_flag },
{ "SO_LINGER", SOL_SOCKET, SO_LINGER, sock_str_linger },
{ "SO_OOBINLINE", SOL_SOCKET, SO_OOBINLINE, sock_str_flag },
{ "SO_RCVBUF", SOL_SOCKET, SO_RCVBUF, sock_str_int },
{ "SO_SNDBUF", SOL_SOCKET, SO_SNDBUF, sock_str_int },
{ "SO_RCVLOWAT", SOL_SOCKET, SO_RCVLOWAT, sock_str_int },
{ "SO_SNDLOWAT", SOL_SOCKET, SO_SNDLOWAT, sock_str_int },
{ "SO_RCVTIMEO", SOL_SOCKET, SO_RCVTIMEO, sock_str_timeval },
{ "SO_SNDTIMEO", SOL_SOCKET, SO_SNDTIMEO, sock_str_timeval },
{ "SO_REUSEADDR", SOL_SOCKET, SO_REUSEADDR, sock_str_flag },
#ifdef SO_REUSEPORT
{ "SO_REUSEPORT", SOL_SOCKET, SO_REUSEPORT, sock_str_flag },
#else
{ "SO_REUSEPORT", 0, 0, NULL },
#endif
{ "SO_TYPE", SOL_SOCKET, SO_TYPE, sock_str_int },
{ "SO_USELOOPBACK", SOL_SOCKET, SO_USELOOPBACK, sock_str_flag },
{ "IP_TOS", IPPROTO_IP, IP_TOS, sock_str_int },
{ "IP_TTL", IPPROTO_IP, IP_TTL, sock_str_int },
#ifdef IPV6_DONTFRAG
{ "IPV6_DONTFRAG", IPPROTO_IPV6,IPV6_DONTFRAG, sock_str_flag },
#else
{ "IPV6_DONTFRAG", 0, 0, NULL },
#endif
#ifdef IPV6_UNICAST_HOPS
{ "IPV6_UNICAST_HOPS", IPPROTO_IPV6,IPV6_UNICAST_HOPS,sock_str_int },
#else
{ "IPV6_UNICAST_HOPS", 0, 0, NULL },
#endif
#ifdef IPV6_V6ONLY
{ "IPV6_V6ONLY", IPPROTO_IPV6,IPV6_V6ONLY, sock_str_flag },
#else
{ "IPV6_V6ONLY", 0, 0, NULL },
#endif
{ "TCP_MAXSEG", IPPROTO_TCP,TCP_MAXSEG, sock_str_int },
{ "TCP_NODELAY", IPPROTO_TCP,TCP_NODELAY, sock_str_flag },
#ifdef SCTP_AUTOCLOSE
{ "SCTP_AUTOCLOSE", IPPROTO_SCTP,SCTP_AUTOCLOSE,sock_str_int },
#else
{ "SCTP_AUTOCLOSE", 0, 0, NULL },
#endif
#ifdef SCTP_MAXBURST
{ "SCTP_MAXBURST", IPPROTO_SCTP,SCTP_MAXBURST, sock_str_int },
#else
{ "SCTP_MAXBURST", 0, 0, NULL },
#endif
#ifdef SCTP_MAXSEG
{ "SCTP_MAXSEG", IPPROTO_SCTP,SCTP_MAXSEG, sock_str_int },
#else
{ "SCTP_MAXSEG", 0, 0, NULL },
#endif
#ifdef SCTP_NODELAY
{ "SCTP_NODELAY", IPPROTO_SCTP,SCTP_NODELAY, sock_str_flag },
#else
{ "SCTP_NODELAY", 0, 0, NULL },
#endif
{ NULL, 0, 0, NULL }
};
/* *INDENT-ON* */
/* end checkopts1 */
/* include checkopts2 */
int
main(int argc, char **argv)
{
int fd;
socklen_t len;
struct sock_opts *ptr;
fd = Socket(AF_INET,SOCK_STREAM,0); //added by liyuan
for (ptr = sock_opts; ptr->opt_str != NULL; ptr++) {
printf("%s: ", ptr->opt_str);
if (ptr->opt_val_str == NULL)
printf("(undefined)\n");
else {
switch(ptr->opt_level) {
case SOL_SOCKET:
case IPPROTO_IP:
case IPPROTO_TCP:
fd = Socket(AF_INET, SOCK_STREAM, 0);
break;
#ifdef IPV6
case IPPROTO_IPV6:
fd = Socket(AF_INET6, SOCK_STREAM, 0);
break;
#endif
#ifdef IPPROTO_SCTP
case IPPROTO_SCTP:
fd = Socket(AF_INET, SOCK_SEQPACKET, IPPROTO_SCTP);
break;
#endif
default:
err_quit("Can't create fd for level %d\n", ptr->opt_level);
}
len = sizeof(val);
if (getsockopt(fd, ptr->opt_level, ptr->opt_name,
&val, &len) == -1) {
err_ret("getsockopt error");
} else {
printf("default = %s\n", (*ptr->opt_val_str)(&val, len));
}
close(fd);
}
}
exit(0);
}
/* end checkopts2 */
/* include checkopts3 */
static char strres[128];
static char *
sock_str_flag(union val *ptr, int len)
{
/* *INDENT-OFF* */
if (len != sizeof(int))
snprintf(strres, sizeof(strres), "size (%d) not sizeof(int)", len);
else
snprintf(strres, sizeof(strres),
"%s", (ptr->i_val == 0) ? "off" : "on");
return(strres);
/* *INDENT-ON* */
}
/* end checkopts3 */
static char *
sock_str_int(union val *ptr, int len)
{
if (len != sizeof(int))
snprintf(strres, sizeof(strres), "size (%d) not sizeof(int)", len);
else
snprintf(strres, sizeof(strres), "%d", ptr->i_val);
return(strres);
}
static char *
sock_str_linger(union val *ptr, int len)
{
struct linger *lptr = &ptr->linger_val;
if (len != sizeof(struct linger))
snprintf(strres, sizeof(strres),
"size (%d) not sizeof(struct linger)", len);
else
snprintf(strres, sizeof(strres), "l_onoff = %d, l_linger = %d",
lptr->l_onoff, lptr->l_linger);
return(strres);
}
static char *
sock_str_timeval(union val *ptr, int len)
{
struct timeval *tvptr = &ptr->timeval_val;
if (len != sizeof(struct timeval))
snprintf(strres, sizeof(strres),
"size (%d) not sizeof(struct timeval)", len);
else
snprintf(strres, sizeof(strres), "%d sec, %d usec",
tvptr->tv_sec, tvptr->tv_usec);
return(strres);
}
7.5 基本套接口选项
以下面的建议来总结对套接口选线的讨论：
1）在所有tcp服务中，在调用bind之前设置SO_REUSEADDR套接口选项；
2）当编写一个同一时刻在同一主机上可运行多次的多播应用程序时，设置SO_REUSEADDR套接口选项，并将本组的多播地址作为本地ip地址绑定。
7.10 fcntl函数int fcntl ( int fd, int cmd, …/* int arg */);
返回： 依赖于参数 cmd , -1 --------出错
每个描述字（包括套接口描述字）都有一组命令F_GETFL取得和F_SETFL设置的文件标志。影响套接口的两个标志是：
O_NONBLOCK -------费阻塞I/O
O_ASYNC -------信号驱动I/O
信号SIGIO和SIGURG与其他信号不同之处是，这两个信号仅在已用命令F_SETOWN给套接口指派了属主后才会生成。
当一个新的套接口由函数socket创建时，它没有属主，但是当一个新的套接口从一个监听套接口创建时，套接口属主便由已连接套接口从监听套接口继承而来（许多套接口选项也这样）。
7.11 小结SO_LINGER套接口选项使我们能更好控制函数close返回的时机，让我们可以强制发送一个RST而不是tcp的四分组连接终止序列。我们必须小心发送RST，因为这避免了tcp的TIME_WAIT状态。也有套接口选项无法提供我们所需要信息的情况，此时就要求有应用级的ACK。
每个tcp套接口都有一个发送缓冲区和一个接受缓冲区，每个udp套接口都有一个接受缓冲区。SO_SNDBUF和SO_RCVBUF套接口选项让我们可以改变这些缓冲区的大小。
