第7章 套接字选项
7.3 检查选项是否受支持并获取默认值
#define __need_timeval
#include <stdio.h>
#include <time.h>
#include <netinet/tcp.h> /* for TCP_xxx defines */
#include <sys/socket.h>
#include <netinet/in.h> /* sockaddr_in{} and other Internet defns */
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <syslog.h> /* for syslog() */
#include <stdarg.h> /* ANSI C header file */
#include <unistd.h>
#define MAXLINE 4096 /* max text line length */
int daemon_proc; /* set nonzero by daemon_init() */
union val {
int i_val;
long l_val;
struct linger linger_val;
struct timeval timeval_val;
} val;
static char strres[128];
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* */
}
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);
}
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);
}
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), "%ld sec, %ld usec",
tvptr->tv_sec, tvptr->tv_usec);
return (strres);
}
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
#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
#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* */
void err_doit(int errnoflag, int level, const char *fmt, va_list ap)
{
int errno_save, n;
char buf[MAXLINE + 1];
errno_save = errno; /* value caller might want printed */
#ifdef HAVE_VSNPRINTF
vsnprintf(buf, MAXLINE, fmt, ap); /* safe */
#else
vsprintf(buf, fmt, ap); /* not safe */
#endif
n = strlen(buf);
if (errnoflag)
snprintf(buf + n, MAXLINE - n, ": %s", strerror(errno_save));
strcat(buf, "\n");
if (daemon_proc) {
syslog(level, "%s", buf);
} else {
fflush(stdout); /* in case stdout and stderr are the same */
fputs(buf, stderr);
fflush(stderr);
}
return;
}
void err_quit(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
err_doit(0, LOG_ERR, fmt, ap);
va_end(ap);
exit(1);
}
void err_sys(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
err_doit(1, LOG_ERR, fmt, ap);
va_end(ap);
exit(1);
}
void err_ret(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
err_doit(1, LOG_INFO, fmt, ap);
va_end(ap);
return;
}
int Socket(int family, int type, int protocol)
{
int n;
if ((n = socket(family, type, protocol)) < 0)
err_sys("socket error");
return (n);
}
int main()
{
int fd;
socklen_t len;
struct sock_opts *ptr;
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);
}
