从c代码打印ip地址和udp端口

Question

我正在使用原始udp套接字。我有一个IP地址和udp端口通过终端插入在以下mannar中分配。 Id喜欢打印出来以经典的字符串格式（例如，192.168.16.2）

ip->iph_sourceip = inet_addr(argv[1]); 
udp->udph_srcport = htons(atoi(argv[2])); 

我tryed printf ("Packet Send. iph_sourceip: %d \n" , ip->iph_sourceip);，但我刚刚得到的随机数。

我也试过printf ("Packet Send. iph_sourceip: %c \n" , inet_ntoa(ip->iph_sourceip));在这里我得到一个奇怪的迹象。他们不工作。

下面是完整的代码：

// ----rawudp.c------ 
// Must be run by root lol! Just datagram, no payload/data 
#include <unistd.h> 
#include <stdio.h> 
#include <sys/socket.h> 
#include <netinet/ip.h> 
#include <netinet/udp.h> 

// The packet length 
#define PCKT_LEN 8192 

// Can create separate header file (.h) for all headers' structure 
// The IP header's structure 
struct ipheader { 
    unsigned char iph_ihl :5, iph_ver :4; 
    unsigned char iph_tos; 
    unsigned short int iph_len; 
    unsigned short int iph_ident; 
    unsigned char iph_flag; 
    unsigned short int iph_offset; 
    unsigned char iph_ttl; 
    unsigned char iph_protocol; 
    unsigned short int iph_chksum; 
    unsigned int iph_sourceip; 
    unsigned int iph_destip; 
}; 

// UDP header's structure 
struct udpheader { 
    unsigned short int udph_srcport; 
    unsigned short int udph_destport; 
    unsigned short int udph_len; 
    unsigned short int udph_chksum; 
}; 
// total udp header length: 8 bytes (=64 bits) 
// Function for checksum calculation. From the RFC, 
// the checksum algorithm is: 
// "The checksum field is the 16 bit one's complement of the one's 
// complement sum of all 16 bit words in the header. For purposes of 
// computing the checksum, the value of the checksum field is zero." 
unsigned short csum(unsigned short *buf, int nwords) { // 
    unsigned long sum; 
    for (sum = 0; nwords > 0; nwords--) 
     sum += *buf++; 
    sum = (sum >> 16) + (sum & 0xffff); 
    sum += (sum >> 16); 
    return (unsigned short) (~sum); 
} 
// Source IP, source port, target IP, target port from the command line arguments 
int main(int argc, char *argv[]) { 
    int sd; 
// No data/payload just datagram 
    char buffer[PCKT_LEN]; 
// Our own headers' structures 
    struct ipheader *ip = (struct ipheader *) buffer; 
    struct udpheader *udp = (struct udpheader *) (buffer 
      + sizeof(struct ipheader)); 
// Source and destination addresses: IP and port 
    struct sockaddr_in sin, din; 
    int one = 1; 
    const int *val = &one; 

    memset(buffer, 0, PCKT_LEN); 

    if (argc != 5) { 
     printf("- Invalid parameters!!!\n"); 
     printf(
       "- Usage %s <source hostname/IP> <source port> <target hostname/IP> <target port>\n", 
       argv[0]); 
     exit(-1); 
    } 

// Create a raw socket with UDP protocol 
    sd = socket(PF_INET, SOCK_RAW, IPPROTO_UDP); 
    if (sd < 0) { 
     perror("socket() error"); 
// If something wrong just exit 
     exit(-1); 
    } else 
     printf("socket() - Using SOCK_RAW socket and UDP protocol is OK.\n"); 

// The source is redundant, may be used later if needed 
// The address family 
    sin.sin_family = AF_INET; 
    din.sin_family = AF_INET; 
// Port numbers 
    sin.sin_port = htons(atoi(argv[2])); 
    din.sin_port = htons(atoi(argv[4])); 
// IP addresses 
    sin.sin_addr.s_addr = inet_addr(argv[1]); 
    din.sin_addr.s_addr = inet_addr(argv[3]); 

// Fabricate the IP header or we can use the 
// standard header structures but assign our own values. 
    ip->iph_ihl = 5; 
    ip->iph_ver = 4; 
    ip->iph_tos = 16; // Low delay 
    ip->iph_len = sizeof(struct ipheader) + sizeof(struct udpheader); 
    ip->iph_ident = htons(54321); 
    ip->iph_ttl = 64; // hops 
    ip->iph_protocol = 17; // UDP 
// Source IP address, can use spoofed address here!!! 
    ip->iph_sourceip = inet_addr(argv[1]); 
// The destination IP address 
    ip->iph_destip = inet_addr(argv[3]); 

// Fabricate the UDP header. Source port number, redundant 
    udp->udph_srcport = htons(atoi(argv[2])); 
// Destination port number 
    udp->udph_destport = htons(atoi(argv[4])); 
    udp->udph_len = htons(sizeof(struct udpheader)); 
// Calculate the checksum for integrity 
    ip->iph_chksum = csum((unsigned short *) buffer, 
      sizeof(struct ipheader) + sizeof(struct udpheader)); 
// Inform the kernel do not fill up the packet structure. we will build our own... 
    if (setsockopt(sd, IPPROTO_IP, IP_HDRINCL, val, sizeof(one)) < 0) { 
     perror("setsockopt() error"); 
     exit(-1); 
    } else 
     printf("setsockopt() is OK.\n"); 

// Send loop, send for every 2 second for 100 count 
    printf("Trying...\n"); 
    printf("Using raw socket and UDP protocol\n"); 
    printf("Using Source IP: %s port: %u, Target IP: %s port: %u.\n", argv[1], 
      atoi(argv[2]), argv[3], atoi(argv[4])); 

    int count; 
    for (count = 1; count <= 20; count++) { 
     if (sendto(sd, buffer, ip->iph_len, 0, (struct sockaddr *) &sin, 
       sizeof(sin)) < 0) 
// Verify 
       { 
      perror("sendto() error"); 
      exit(-1); 
     } else { 
      printf("Count #%u - sendto() is OK.\n", count); 
      printf ("Packet Send. iph_sourceip: %s \n" , inet_ntoa(ip->iph_sourceip)); 
      sleep(2); 
     } 
    } 
    close(sd); 
    return 0; 
} 

Answer 1

您需要使用inet_ntoa()功能的网络秩序的二进制数据转换为点分十进制格式（在线路138中的printf IM感兴趣的），然后你”已经使用%s格式说明符来打印结果。

Answer 2

IP地址是一个字符串，需要用％s打印。