nmap 路由解析
一、获取系统中所有的网络接口的方法
方法１．读取/proc/net/dev
intf_loop(intf_t *intf, intf_handler callback, void *arg)//按行读取/proc/net/dev,来获取接口名
{
FILE *fp;
struct intf_entry *entry;
char *p, buf[BUFSIZ], ebuf[BUFSIZ];
int ret;
if ((fp = fopen(PROC_DEV_FILE, "r")) == NULL)//#define PROC_DEV_FILE "/proc/net/dev"
return (-1);
...
while (fgets(buf, sizeof(buf), fp) != NULL) { //按行读取/proc/net/dev
if ((p = strchr(buf, ':')) == NULL) //遇到：，则保存指针
continue;
*p = '\0'; //在原先‘:‘ 的位置，存入'\0'，截断字符串
for (p = buf; *p == ' '; p++) //去掉多余的空格
;
}
if (_intf_get_noalias(intf, entry) < 0) {
ret = -1;
break;
}
....
return (ret);
}
写一段小程序，理解这里的字符串截取
char buf[] = "123:456";
char *p;
p = strchr(buf,':');
*p = '\0';
printf("buf is %s\n",buf);
输出结果buf is 123
方法２、利用ioctl
int
intf_loop(intf_t *intf, intf_handler callback, void *arg)
{
struct intf_entry *entry;
struct ifreq *ifr, *lifr, *pifr;
char *p, ebuf[BUFSIZ];
int ret;
entry = (struct intf_entry *)ebuf;
intf->ifc.ifc_buf = (caddr_t)intf->ifcbuf;
intf->ifc.ifc_len = sizeof(intf->ifcbuf);
if (ioctl(intf->fd, SIOCGIFCONF, &intf->ifc) < 0)
return (-1);
pifr = NULL;
lifr = (struct ifreq *)&intf->ifc.ifc_buf[intf->ifc.ifc_len];//指向ifc.ifc_buf数组的最后位置
for (ifr = intf->ifc.ifc_req; ifr < lifr; ifr = NEXTIFR(ifr)) {//指针的增加，
strcmp(ifr->ifr_name, pifr->ifr_name);
这里，使用指针直接增加。看到过两种：
上面是一种，是
ifr->ifr_addr +max(ifr->ifr_addr.sa_len, sizeof(struct sockaddr))
是直接用ip地址位置 + ip地址长度。
其中max因为有ipv4 ipv6两种，其中，ipv4的sa_len和sizeof(struct sockaddr)是一样大的，而ipv6的 sa_len > sizeof(struct sockaddr)
第二种，是ifr +ifr_name长度+ ip 地址长度
for( ifr = ifc.ifc_req; ifr < buf +ifc.ifc_len; )
{
ifr +=sizeof(ifr->ifr_name)+max(ifr->ifr_addr.sa_len, sizeof(struct sockaddr));
}
这两种方法，试过总出问题，并且提示sockaddr没有sa_len成员
第三种是直接计数，这中方法是要点是 １．struct ifreq *buf; ２．buf[i].ifr_name
struct ifreq *buf;
if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
return -1;
buf = malloc(10*sizeof(struct ifreq));
memset(buf, 0 ,10*sizeof(struct ifreq));
ifc.ifc_len = 10 *sizeof(struct ifreq);
ifc.ifc_req = buf;
ioctl(fd,SIOCGIFCONF, &ifc);
lifr = (struct ifreq*)&ifc.ifc_buf[ifc.ifc_len];
count = ifc.ifc_len/(sizeof(struct ifreq));
for(i=0; i< count;i++)
{
printf("intf %s\n",buf[i].ifr_name);
}
close(fd);
_intf_get_noalias(intf_t *intf, struct intf_entry *entry)
{
struct ifreq ifr;
/* Get interface index. */
entry->intf_index = if_nametoindex(entry->intf_name);//通过接口名获得接口索引
if (entry->intf_index == 0)
return (-1);
strlcpy(ifr.ifr_name, entry->intf_name, sizeof(ifr.ifr_name));
/* Get interface flags. */
if (ioctl(intf->fd, SIOCGIFFLAGS, &ifr) < 0)
return (-1);
entry->intf_flags = intf_iff_to_flags(ifr.ifr_flags);
_intf_set_type(entry);
/* Get interface MTU. */
#ifdef SIOCGIFMTU
if (ioctl(intf->fd, SIOCGIFMTU, &ifr) < 0)
#endif
return (-1);
entry->intf_mtu = ifr.ifr_mtu;
entry->intf_addr.addr_type = entry->intf_dst_addr.addr_type =
entry->intf_link_addr.addr_type = ADDR_TYPE_NONE;
/* Get primary interface address. */
if (ioctl(intf->fd, SIOCGIFADDR, &ifr) == 0) {
addr_ston(&ifr.ifr_addr, &entry->intf_addr);
if (ioctl(intf->fd, SIOCGIFNETMASK, &ifr) < 0)
return (-1);
addr_stob(&ifr.ifr_addr, &entry->intf_addr.addr_bits);
}
/* Get other addresses. */
if (entry->intf_type == INTF_TYPE_TUN) {
if (ioctl(intf->fd, SIOCGIFDSTADDR, &ifr) == 0) {
if (addr_ston(&ifr.ifr_addr,
&entry->intf_dst_addr) < 0)
return (-1);
}
} else if (entry->intf_type == INTF_TYPE_ETH) {
#if defined(SIOCGIFHWADDR)
if (ioctl(intf->fd, SIOCGIFHWADDR, &ifr) < 0)
return (-1);
if (addr_ston(&ifr.ifr_addr, &entry->intf_link_addr) < 0)
return (-1);
#elif defined(SIOCRPHYSADDR)
/* Tru64 */
struct ifdevea *ifd = (struct ifdevea *)
size_t
strlcpy(dst, src, siz)
char *dst;
const char *src;
size_t siz;
{
register char *d = dst;
register const char *s = src;
register size_t n = siz;
/* Copy as many bytes as will fit */
if (n != 0 && --n != 0) { //判断n是否为0，或1，同时这样的--n也为字符串末尾的'\0'空出位置
do {
if ((*d++ = *s++) == 0)
break;
} while (--n != 0);
}
/* Not enough room in dst, add NUL and traverse rest of src */
if (n == 0) {
if (siz != 0)
*d = '\0'; /* NUL-terminate dst */
while (*s++)
;
}
return(s - src - 1); /* count does not include NUL */
}