ip层和4层的接口实现分析
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L4的协议都是在linux/in.h这个文件中,都是以IPPROTO开头的一些宏.由于ip头中的4层协议域是8位,因此4层协议的最大数值也就是255.而在内核中,255是raw ip, IPPPROTO_RAW:
Java代码
enum {
IPPROTO_IP = 0, /* Dummy protocol for TCP */
IPPROTO_ICMP = 1, /* Internet Control Message Protocol */
IPPROTO_IGMP = 2, /* Internet Group Management Protocol */
IPPROTO_IPIP = 4, /* IPIP tunnels (older KA9Q tunnels use 94) */
IPPROTO_TCP = 6, /* Transmission Control Protocol */
IPPROTO_EGP = 8, /* Exterior Gateway Protocol */
IPPROTO_PUP = 12, /* PUP protocol */
IPPROTO_UDP = 17, /* User Datagram Protocol */
IPPROTO_IDP = 22, /* XNS IDP protocol */
IPPROTO_DCCP = 33, /* Datagram Congestion Control Protocol */
IPPROTO_RSVP = 46, /* RSVP protocol */
IPPROTO_GRE = 47, /* Cisco GRE tunnels (rfc 1701,1702) */
IPPROTO_IPV6 = 41, /* IPv6-in-IPv4 tunnelling */
IPPROTO_ESP = 50, /* Encapsulation Security Payload protocol */
IPPROTO_AH = 51, /* Authentication Header protocol */
IPPROTO_BEETPH = 94, /* IP option pseudo header for BEET */
IPPROTO_PIM = 103, /* Protocol Independent Multicast */
IPPROTO_COMP = 108, /* Compression Header protocol */
IPPROTO_SCTP = 132, /* Stream Control Transport Protocol */
IPPROTO_UDPLITE = 136, /* UDP-Lite (RFC 3828) */
IPPROTO_RAW = 255, /* Raw IP packets */
IPPROTO_MAX
};
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