Setting IPv4/IPv6 address and port to a sockaddr_storage structure

c++, ip-address, ipv6, sockets

Solution

I highly recommend letting `getaddrinfo` do all the heavy lifting, eg.

void DataSocket::SetLocalAddr(const char *addr, const unsigned short int port)
{
    struct addrinfo hints, *res;
    int status;
    char port_buffer[6];

    sprintf(port_buffer, "%hu", port);

    memset(&hints, 0, sizeof(hints));
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    /* Setting AI_PASSIVE will give you a wildcard address if addr is NULL */
    hints.ai_flags = AI_NUMERICHOST | AI_NUMERICSERV | AI_PASSIVE;

    if ((status = getaddrinfo(addr, port_buffer, &hints, &res) != 0)
    {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(status));
        return;
    }

    /* Note, we're taking the first valid address, there may be more than one */
    memcpy(&this->laddr, res->ai_addr, res->ai_addrlen);

    freeaddrinfo(res);
}

Problem

I'm porting a IPv4 application to a AF-independent codebase(it should work with IPv4 and IPv6). Now I'm using sockaddr_storage wherever I can, however now I have to set(populate) a sockaddr_storage. But I don't know what the correct way is. The previous code was: ``` // defined in data_socket.h struct sockaddr_in laddr; ``` Now there is this function that sets sin_addr and sin_port: ``` void DataSocket::SetLocalAddr(const char *addr, const int port) { this->laddr.sin_port = htons(port); if(addr != NULL) this->laddr.sin_addr.s_addr = inet_addr(addr); else this->laddr.sin_addr.s_addr = inet_addr("0.0.0.0"); } ``` As you see this is the old style(uses IPv4). Now my changes are below. First I've changed `sockaddr_in` to `sockaddr_storage` ``` // defined in data_socket.h struct sockaddr_storage laddr; ``` Then I changed the code above to support IPv4 and IPv6: ``` void DataSocket::SetLocalAddr(const char *addr, const int port) { switch (this->GetAddrFamily(addr)) { case AF_INET: (struct sockaddr_in *) this->laddr.sin_port = htons(port); if(addr != NULL) inet_pton(AF_INET, addr, (struct sockaddr_in *) this->laddr.sin_addr); else inet_pton(AF_INET, "0.0.0.0", (struct sockaddr_in *) this->laddr.sin_addr); break; case AF_INET6: (struct sockaddr_in6 *) this->laddr.sin6_port = htons(port); if(addr != NULL) inet_pton(AF_INET6, addr, (struct sockaddr_in6 *) this->laddr.sin6_addr); else inet_pton(AF_INET6, "0:0:0:0:0:0:0:0", (struct sockaddr_in6 *) this->laddr.sin6_addr); break; default: return NULL; } ``` } Where `GetAddrFamily()` is: ``` int DataSocket::GetAddrFamily(const char *addr) { struct addrinfo hints, *res; int status, result; memset(&hints, 0, sizeof(hints)); hints.ai_family = AF_UNSPEC; hints.ai_socktype = SOCK_STREAM; if ((status = getaddrinfo(addr, 0, &hints, &res)) != 0) { fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(status)); return false; } result = res->ai_family; // This might be AF_INET, AF_INET6,etc.. freeaddrinfo(res); // We're done with res, free it up return result; } ``` It seems my way is to complex. Is this the correct way to do this? Because I've changed sockaddr_in to sockaddr_storage, actually I just want the reverse of this question: Getting IPV4 address from a sockaddr structure I'm trying to find the best solution, for example here: http://www.kame.net/newsletter/19980604/ it says never use `inet_ntop()` and `inet_pton()`, however some others(like the Beej's network tutorial) says that `inet_ntop()` and `inet_pton()` should be used for IPv6 based application. Is my way of implementation correct or should I change it?

Original source

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