iOS Multipath BSD Sockets Test. Comments welcomed!

test.c

# include <sys/types.h>
# include <sys/socket.h>
# include <ifaddrs.h>
# include <arpa/inet.h>
# include <netinet/in.h>

// Bad dirty quick functions written by hot fingers:

char* ipToStr(sockaddr* addr) {
    static char ip[32];
    sprintf(ip, "%d.%d.%d.%d", (unsigned char)addr->sa_data[2], (unsigned char)addr->sa_data[3], (unsigned char)addr->sa_data[4], (unsigned char)addr->sa_data[5]);
    return ip;
}

// so on...
char* ip32ToStr(int addr) {
    static char ip[32];
    char* bytes = (char*)&addr;
    sprintf(ip, "%d.%d.%d.%d", (unsigned char)bytes[3], (unsigned char)bytes[2], (unsigned char)bytes[1], (unsigned char)bytes[0]);
    return ip;
}

// Look here:
void test_stun_ip_multipath_ios() {
    
    ifaddrs* addrs = 0;
    getifaddrs(&addrs);
    
    sockaddr* clt1 = 0;
    sockaddr* clt2 = 0;
    
    while(addrs) {
        char* ip = ipToStr(addrs->ifa_addr);
        fprintf(stderr, "%s: %s\n", addrs->ifa_name, ip);
        
        // FIX THIS ACCORDING YOUR ACTUAL Wi-Fi and 3G IP Addresses:
        if (0 == strncmp("192.168.", ip, 8) ) {
            clt1 = addrs->ifa_addr;
        } else if (0 == strncmp("10.", ip, 3) ) {
            clt2 = addrs->ifa_addr;
        }

        addrs = addrs->ifa_next;
    }

    int sock1 = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    int sock2 = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    
    sockaddr_in cltAddr = {0};
    cltAddr.sin_family = AF_INET;
    cltAddr.sin_port = htons(5555);
     
    // This binds to the enumerated addresses.
    // Auto-assigned ports could be acquired by getsockname, i.e.,
    // int nLen = sizeof(serverAddr);
    // getsockname(sock, (sockaddr*)&serverAddr, &nLen);
    // int recvOnPort = ntohs(serverAddr.sin_port);
    // printf("My port: %d\n", recvOnPort);
    int res1 = bind(sock1, (struct sockaddr *)clt1, sizeof(sockaddr_in));
    int res2 = bind(sock2, (struct sockaddr *)clt2, sizeof(sockaddr_in));


    sockaddr_in serverAddr = {0};
    serverAddr.sin_family = AF_INET;

    // A STUN server (I forgot whom)
    serverAddr.sin_addr.s_addr = inet_addr("23.21.150.121");
    serverAddr.sin_port = htons(3478);
    
    struct StunRequest
    {
        uint16_t msgType;
        uint16_t payloadLen;
        uint32_t magic;
        uint8_t transaction[12];
    };
    
    StunRequest r = {0};
    r.msgType = 0x0100;
    r.payloadLen = 0;
    r.magic = 0x42A41221;
    r.transaction[0] = 5;
    r.transaction[5] = 7;
    
    // Send thru ONE SOCKET
    int sentBytes = sendto(sock1, (char*)&r, sizeof(r), 0,
                           (sockaddr*)&serverAddr, sizeof(serverAddr));
    
    // Send thru ANOTHER SOCKET
    int sentBytes2 = sendto(sock2, (char*)&r, sizeof(r), 0,
                           (sockaddr*)&serverAddr, sizeof(serverAddr));
    
    char recvBuffer[ 1280 ] = {0};
    
    sockaddr_in from = {0};
    socklen_t fromLen = sizeof(from);
    ssize_t nrecvd = recvfrom(sock1, (void*)recvBuffer, sizeof(recvBuffer),
                          0, (sockaddr*)&from, &fromLen);
    
    uint16_t externalPort = ntohs(*((uint16_t*)&recvBuffer[26]));// ^ 0x2112;
    uint32_t externalIp = ntohl(*((uint32_t*)&recvBuffer[28]));// ^ 0x2112A442;
    
    char* extIp1 = ip32ToStr(externalIp);
    fprintf(stderr, "External IP1: %s", extIp1);
    
    nrecvd = recvfrom(sock2, (void*)recvBuffer, sizeof(recvBuffer),
                              0, (sockaddr*)&from, &fromLen);
    
    externalPort = ntohs(*((uint16_t*)&recvBuffer[26]));// ^ 0x2112;
    externalIp = ntohl(*((uint32_t*)&recvBuffer[28]));// ^ 0x2112A442;
    
    char* extIp2 = ip32ToStr(externalIp);
    fprintf(stderr, "External IP2: %s", extIp2);
}

Hi @shivintu ,
Hope you have read the comment // FIX THIS ACCORDING YOUR ACTUAL Wi-Fi and 3G IP Addresses
carefully: you need two different IP addresses. Never bind to 0.0.0.0.
Which version of iOS you have used?

Hi @avesus,

I need to make HTTP request on 2G/3g/4g only in iOS. In android its possible using connectivityManager trying to do the same in iOS but no luck.

If device is connected to Wifi and mobile data both, I need to check and make HTTP request over mobile network.
I know it is not possible to do with the high level API's. But with low-level APIs I can force a particular TCP connection to run over a particular interface, which allows this sort of thing.
Please provide a recommended solution for the same.

Regards,
Bhawna

Hi @BhawnaBhandari24,

Please, enumerate interfaces, obtain the last IP addresses, and re-bind sockets.

Hi, @avesus
I have used above code to make use of wifi and cellular interfaces in parallel.
But it don't work in Network Extensions(Packet Tunnel). I receive errno 49.
Please provide a recommended solution for me, Thanks!

Regards,
Kevinhao

@haojingjing2018 Did you got any solution? I am facing the same problem right now.