c ip报文

C语言中处理IP报文的方法如下：

1. 定义IP报文头结构体

struct ip_header {
    uint8_t version_and_header_length;
    uint8_t type_of_service;
    uint16_t total_length;
    uint16_t identification;
    uint16_t flags_and_fragment_offset;
    uint8_t time_to_live;
    uint8_t protocol;
    uint16_t header_checksum;
    uint32_t source_address;
    uint32_t destination_address;
};

2. 解析IP报文头

struct ip_header *ip = (struct ip_header *) packet;
int version = (ip->version_and_header_length >> 4) & 0x0f;
int header_length = (ip->version_and_header_length & 0x0f) * 4;
int protocol = ip->protocol;
char *source_address = inet_ntoa((struct in_addr){ip->source_address});
char *destination_address = inet_ntoa((struct in_addr){ip->destination_address});

3. 发送IP报文

int sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_RAW);
struct sockaddr_in destination;
destination.sin_family = AF_INET;
destination.sin_addr.s_addr = inet_addr("192.168.1.1");
sendto(sockfd, packet, packet_length, 0, (struct sockaddr *)&destination, sizeof(destination));

以上是处理IP报文的基本方法，具体实现需要根据具体需求进行调整。