郁闷的libnet API设计
看以下两个函数的源代码:
(1)构建ipv4 header的函数
libnet_ptag_t
libnet_build_ipv4(u_int16_t len, u_int8_t tos, u_int16_t id, u_int16_t frag,
u_int8_t ttl, u_int8_t prot, u_int16_t sum, u_int32_t src, u_int32_t dst,
u_int8_t *payload, u_int32_t payload_s, libnet_t *l, libnet_ptag_t ptag)
{
ip_hdr.ip_tos = tos; /* IP tos */
ip_hdr.ip_len = htons(h); /* total length */
ip_hdr.ip_id = htons(id); /* IP ID */
ip_hdr.ip_off = htons(frag); /* fragmentation flags */
ip_hdr.ip_ttl = ttl; /* time to live */
ip_hdr.ip_p = prot; /* transport protocol */
ip_hdr.ip_sum = (sum ? htons(sum) : 0); /* checksum */
ip_hdr.ip_src.s_addr = src; /* source ip */
ip_hdr.ip_dst.s_addr = dst; /* destination ip */
}
libnet_build_ipv4(u_int16_t len, u_int8_t tos, u_int16_t id, u_int16_t frag,
u_int8_t ttl, u_int8_t prot, u_int16_t sum, u_int32_t src, u_int32_t dst,
u_int8_t *payload, u_int32_t payload_s, libnet_t *l, libnet_ptag_t ptag)
{
ip_hdr.ip_tos = tos; /* IP tos */
ip_hdr.ip_len = htons(h); /* total length */
ip_hdr.ip_id = htons(id); /* IP ID */
ip_hdr.ip_off = htons(frag); /* fragmentation flags */
ip_hdr.ip_ttl = ttl; /* time to live */
ip_hdr.ip_p = prot; /* transport protocol */
ip_hdr.ip_sum = (sum ? htons(sum) : 0); /* checksum */
ip_hdr.ip_src.s_addr = src; /* source ip */
ip_hdr.ip_dst.s_addr = dst; /* destination ip */
}
(2)构建udp header的函数
libnet_ptag_t
libnet_build_udp(u_int16_t sp, u_int16_t dp, u_int16_t len, u_int16_t sum,
u_int8_t *payload, u_int32_t payload_s, libnet_t *l, libnet_ptag_t ptag)
{
udp_hdr.uh_sport = htons(sp); /* source port */
udp_hdr.uh_dport = htons(dp); /* destination port */
udp_hdr.uh_ulen = htons(h); /* total length of UDP packet*/
udp_hdr.uh_sum = (sum ? htons(sum) : 0);/* checksum */
}
libnet_build_udp(u_int16_t sp, u_int16_t dp, u_int16_t len, u_int16_t sum,
u_int8_t *payload, u_int32_t payload_s, libnet_t *l, libnet_ptag_t ptag)
{
udp_hdr.uh_sport = htons(sp); /* source port */
udp_hdr.uh_dport = htons(dp); /* destination port */
udp_hdr.uh_ulen = htons(h); /* total length of UDP packet*/
udp_hdr.uh_sum = (sum ? htons(sum) : 0);/* checksum */
}
其中,第一个函数中,ip参数需要以网络字节序传入,第二个函数中,端口参数需要以本机字节序传入。真是一个别扭啊。写程序,又是抓包,又是打印字节,折腾了很长时间才确定不是我的代码有问题,而是libnet1.1.*有缺陷。
版权所有,欢迎转载