1 Reply
      Latest reply: Nov 21, 2016 1:37 AM by eskimo RSS
      waterfall Level 1 Level 1 (0 points)

        I found a reference (http://www.tenouk.com/Module43a.html) for using raw sockets to send a simple UDP packet in Linux, but I cannot get it to work on macOS Sierra10.12.1. I've tried a number of different variations, but sendto() always returns Invalid argument.

         

        I'd be grateful if you could point out my mistake.

         

        Thanks!

         

        #include <iostream>
        #include <unistd.h>
        #include <stdio.h>
        #include <sys/socket.h>
        #include <netinet/ip.h>
        #include <netinet/udp.h>
        #include <arpa/inet.h>
        
        #define PCKT_LEN 8192
        
        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;
        };
        
        struct udpheader {
            unsigned short int udph_srcport;
            unsigned short int udph_destport;
            unsigned short int udph_len;
            unsigned short int udph_chksum;
        };
        
        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);
        }
        
        int main(int argc, char *argv[])
        {
            int sd;
            char buffer[PCKT_LEN], *data;  
        
            struct ipheader *ip = (struct ipheader *) buffer;
            struct udpheader *udp = (struct udpheader *) (buffer + sizeof(struct ipheader));
            data = ((char *)udp + sizeof(struct udpheader));
            struct sockaddr_in sin, din;
            int one = 1;
            const int *val = &one;
        
            memset(buffer, 0, PCKT_LEN);
        
            printf("*** start Debug ***\n");
            printf("char: %lu\n", sizeof(char));
            printf("short: %lu\n", sizeof(short));
            printf("unsigned short: %lu\n", sizeof(unsigned short));
            printf("int: %lu\n", sizeof(int));
            printf("unsigned int: %lu\n", sizeof(unsigned int));
            printf("long: %lu\n", sizeof(long));
            printf("unsigned long: %lu\n", sizeof(unsigned long));
            printf("*** end Debug ***\n");
        
            /*
            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);
            }
            int srcPort = atoi(argv[2]);
            int destPort = atoi(argv[4]);
            char *str_srcIP = argv[1];
            char *str_destIP = argv[3];
            */
        
            int srcPort = 23;
            int destPort = 23;
            char str_srcIP[] = "192.168.1.72";
            char str_destIP[] = "192.168.1.73";
        
            sd = socket(PF_INET, SOCK_RAW, IPPROTO_UDP);
            if(sd < 0)
            {
                perror("socket() error");
                exit(-1);
            }
            else
                printf("socket() - Using SOCK_RAW socket and UDP protocol is OK.\n");
        
            sin.sin_len = sizeof(sin);
            din.sin_len = sizeof(din);
            sin.sin_family = AF_INET;
            din.sin_family = AF_INET;
        
            sin.sin_port = htons(srcPort);
            din.sin_port = htons(destPort);
        
            sin.sin_addr.s_addr = inet_addr(str_srcIP);
            din.sin_addr.s_addr = inet_addr(str_destIP);
        
            strcpy(data, "A");
        
            unsigned long payloadSize = sizeof(struct ipheader) + sizeof(struct udpheader) + strlen(data);
        
            ip->iph_ihl = 5;
            ip->iph_ver = 4;
            ip->iph_tos = 0;
            ip->iph_len = payloadSize;
            ip->iph_ident = htons(54321);
            ip->iph_ttl = 64;
            ip->iph_protocol = IPPROTO_UDP;
            ip->iph_sourceip = inet_addr(str_srcIP);
            ip->iph_destip = inet_addr(str_destIP);
        
            udp->udph_srcport = htons(srcPort);
            udp->udph_destport = htons(destPort);
            udp->udph_len = htons(sizeof(struct udpheader));
        
            ip->iph_chksum = csum((unsigned short *)buffer, sizeof(struct ipheader) + sizeof(struct udpheader));
        
            if(setsockopt(sd, IPPROTO_IP, IP_HDRINCL, val, sizeof(one)) < 0)
            {
                perror("setsockopt() error");
                exit(-1);
            }
            else
                printf("setsockopt() is OK.\n");
        
            printf("Trying...\n");
            printf("Using raw socket and UDP protocol\n");
            printf("Using Source IP: %s port: %u, Target IP: %s port: %u.\n", str_srcIP, srcPort, str_destIP, destPort);
        
            std::cout<<"*** start Debug ***"<<std::endl;
            std::cout<<"sd: "<<sd<<std::endl;
            std::cout<<"Buffer: "<<buffer<<std::endl;
            std::cout<<"iph_len: "<<ip->iph_len<<std::endl;
            std::cout<<"sin: "<<(struct sockaddr *)&sin<<std::endl;
            std::cout<<"sizeof(sin): "<<sizeof(sin)<<std::endl;
            std::cout<<"*** end Debug ***"<<std::endl;
        
            int count;
            for(count = 1; count <=20; count++)
            {
                if(sendto(sd, buffer, ip->iph_len, 0, (struct sockaddr *)&sin, sizeof(sin)) < 0)
                {
                    perror("sendto() error");
                    exit(-1);
                }
                else
                {
                    printf("Count #%u - sendto() is OK.\n", count);
                    sleep(2);
                }
            }
            close(sd);
            return 0;
        }