ifconfig 源码分析
来源:互联网 发布:office 2013 mac 编辑:程序博客网 时间:2024/05/01 00:45
int main(int argc, char **argv)
{
……
argc--;
argv++;
while (argc && *argv[0] == '-')
{
……
}
打开内核支持的所有协议的套接字,主要是一个循环调用socket的过程
if ((skfd = sockets_open(0)) < 0)
{
perror("socket");
exit(1);
}
if (argc == 0)
{
int err = if_print((char *) NULL);
(void) close(skfd);
exit(err < 0);
}
spp = argv;
safe_strncpy(ifr.ifr_name, *spp++, IFNAMSIZ);
if (*spp == (char *) NULL)
{
int err = if_print(ifr.ifr_name);
(void) close(skfd);
exit(err < 0);
}
if ((ap = get_aftype(*spp)) != NULL)
spp++;
else
ap = get_aftype(DFLT_AF);
if (ap)
{
addr_family = ap->af;
skfd = ap->fd;
}
while (*spp != (char *) NULL)
{
}
switch (ap->af)
{
……
r = ioctl(fd, SIOCSIFADDR, &ifr);
……
}
在主函数中判断argc,如果仅仅是输入了ifconfig而没有任何参数,则输出全部网卡信息
if (argc == 0)
{
int err = if_print((char *) NULL);
(void) close(skfd);
exit(err < 0);
}
函数if_print 定义在ifconfig.c中,用来输出网卡地址等信息:
static int if_print(char *ifname)
{
int res;
if (ife_short) //如果是以省略模式输出
printf(_("Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg/n"));
if (!ifname)
{
//如果ifname==NULL,则表示输出全部网卡的信息
res = for_all_interfaces(do_if_print, &opt_a);
}
else {
//否则仅仅输出ifname的。
struct interface *ife;
ife = lookup_interface(ifname);
res = do_if_fetch(ife);
if (res >= 0)
ife_print(ife);
}
return res;
}
这里,又涉及到两个函数的调用:for_all_interfaces和lookup_interface。先来看for_all_interfaces
函数在interface.c中实现:
参数int (*doit) (struct interface *, void *)是一个指向函数的指针,为实际的功能函数,在上层函数中传递过来的是do_if_print
int for_all_interfaces(int (*doit) (struct interface *, void *), void *cookie)
{
struct interface *ife;
if (!int_list && (if_readlist() < 0))
return -1;
for (ife = int_list; ife; ife = ife->next) {
int err = doit(ife, cookie); //调用函数do_if_print实现
if (err)
return err;
}
return 0;
}
int do_if_print(struct interface *ife, void *cookie)
{
int *opt_a = (int *) cookie;
int res;
res = do_if_fetch(ife); //提取出网卡的信息,置于结构ife中,顺便检查一下设备的合法性,如是否存在等等……
if (res >= 0) {
if ((ife->flags & IFF_UP) || *opt_a)
ife_print(ife); //输出
}
return res;
}
int do_if_fetch(struct interface *ife)
{
if (if_fetch(ife) < 0) {
char *errmsg;
if (errno == ENODEV) {
errmsg = _("Device not found");
} else {
errmsg = strerror(errno);
}
fprintf(stderr, _("%s: error fetching interface information: %s/n"),
ife->name, errmsg);
return -1;
}
return 0;
}
int if_fetch(struct interface *ife)
{
struct ifreq ifr;
int fd;
char *ifname = ife->name;
strcpy(ifr.ifr_name, ifname);
if (ioctl(skfd, SIOCGIFFLAGS, &ifr) < 0)
return (-1);
ife->flags = ifr.ifr_flags;
strcpy(ifr.ifr_name, ifname);
if (ioctl(skfd, SIOCGIFHWADDR, &ifr) < 0)
memset(ife->hwaddr, 0, 32);
else
memcpy(ife->hwaddr, ifr.ifr_hwaddr.sa_data, 8);
ife->type = ifr.ifr_hwaddr.sa_family;
strcpy(ifr.ifr_name, ifname);
if (ioctl(skfd, SIOCGIFMETRIC, &ifr) < 0)
ife->metric = 0;
else
ife->metric = ifr.ifr_metric;
strcpy(ifr.ifr_name, ifname);
if (ioctl(skfd, SIOCGIFMTU, &ifr) < 0)
ife->mtu = 0;
else
ife->mtu = ifr.ifr_mtu;
#ifdef HAVE_HWSLIP
if (ife->type == ARPHRD_SLIP || ife->type == ARPHRD_CSLIP ||
ife->type == ARPHRD_SLIP6 || ife->type == ARPHRD_CSLIP6 ||
ife->type == ARPHRD_ADAPT) {
#ifdef SIOCGOUTFILL
strcpy(ifr.ifr_name, ifname);
if (ioctl(skfd, SIOCGOUTFILL, &ifr) < 0)
ife->outfill = 0;
else
ife->outfill = (unsigned int) ifr.ifr_data;
#endif
#ifdef SIOCGKEEPALIVE
strcpy(ifr.ifr_name, ifname);
if (ioctl(skfd, SIOCGKEEPALIVE, &ifr) < 0)
ife->keepalive = 0;
else
ife->keepalive = (unsigned int) ifr.ifr_data;
#endif
}
#endif
strcpy(ifr.ifr_name, ifname);
if (ioctl(skfd, SIOCGIFMAP, &ifr) < 0)
memset(&ife->map, 0, sizeof(struct ifmap));
else
memcpy(&ife->map, &ifr.ifr_map, sizeof(struct ifmap));
strcpy(ifr.ifr_name, ifname);
if (ioctl(skfd, SIOCGIFMAP, &ifr) < 0)
memset(&ife->map, 0, sizeof(struct ifmap));
else
ife->map = ifr.ifr_map;
#ifdef HAVE_TXQUEUELEN
strcpy(ifr.ifr_name, ifname);
if (ioctl(skfd, SIOCGIFTXQLEN, &ifr) < 0)
ife->tx_queue_len = -1;
else
ife->tx_queue_len = ifr.ifr_qlen;
#else
ife->tx_queue_len = -1;
#endif
#if HAVE_AFINET
fd = get_socket_for_af(AF_INET);
if (fd >= 0) {
strcpy(ifr.ifr_name, ifname);
ifr.ifr_addr.sa_family = AF_INET;
if (ioctl(fd, SIOCGIFADDR, &ifr) == 0) {
ife->has_ip = 1;
ife->addr = ifr.ifr_addr;
strcpy(ifr.ifr_name, ifname);
if (ioctl(fd, SIOCGIFDSTADDR, &ifr) < 0)
memset(&ife->dstaddr, 0, sizeof(struct sockaddr));
else
ife->dstaddr = ifr.ifr_dstaddr;
strcpy(ifr.ifr_name, ifname);
if (ioctl(fd, SIOCGIFBRDADDR, &ifr) < 0)
memset(&ife->broadaddr, 0, sizeof(struct sockaddr));
else
ife->broadaddr = ifr.ifr_broadaddr;
strcpy(ifr.ifr_name, ifname);
if (ioctl(fd, SIOCGIFNETMASK, &ifr) < 0)
memset(&ife->netmask, 0, sizeof(struct sockaddr));
else
ife->netmask = ifr.ifr_netmask;
} else
memset(&ife->addr, 0, sizeof(struct sockaddr));
}
#endif
#if HAVE_AFATALK
fd = get_socket_for_af(AF_APPLETALK);
if (fd >= 0) {
strcpy(ifr.ifr_name, ifname);
if (ioctl(fd, SIOCGIFADDR, &ifr) == 0) {
ife->ddpaddr = ifr.ifr_addr;
ife->has_ddp = 1;
}
}
#endif
#if HAVE_AFIPX
fd = get_socket_for_af(AF_IPX);
if (fd >= 0) {
strcpy(ifr.ifr_name, ifname);
if (!ipx_getaddr(fd, IPX_FRAME_ETHERII, &ifr)) {
ife->has_ipx_bb = 1;
ife->ipxaddr_bb = ifr.ifr_addr;
}
strcpy(ifr.ifr_name, ifname);
if (!ipx_getaddr(fd, IPX_FRAME_SNAP, &ifr)) {
ife->has_ipx_sn = 1;
ife->ipxaddr_sn = ifr.ifr_addr;
}
strcpy(ifr.ifr_name, ifname);
if (!ipx_getaddr(fd, IPX_FRAME_8023, &ifr)) {
ife->has_ipx_e3 = 1;
ife->ipxaddr_e3 = ifr.ifr_addr;
}
strcpy(ifr.ifr_name, ifname);
if (!ipx_getaddr(fd, IPX_FRAME_8022, &ifr)) {
ife->has_ipx_e2 = 1;
ife->ipxaddr_e2 = ifr.ifr_addr;
}
}
#endif
#if HAVE_AFECONET
fd = get_socket_for_af(AF_ECONET);
if (fd >= 0) {
strcpy(ifr.ifr_name, ifname);
if (ioctl(fd, SIOCGIFADDR, &ifr) == 0) {
ife->ecaddr = ifr.ifr_addr;
ife->has_econet = 1;
}
}
#endif
return 0;
}
ife_print 仅仅是根据标志来判断是省略模式输出还是详细模式输出:
void ife_print(struct interface *i)
{
if (ife_short)
ife_print_short(i);
else
ife_print_long(i);
}
以详细模式为例,其实就是一个printf 的过程,读取后的参数都放在结构struct interface 中……大家可以对照Linux 中输出命令look一下就明白了!
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