Question

我有这段代码连接到本地石墨（实际上只是nc -l -p 2023在localhost上运行）：

getCarbonAddr :: Config -> IO SockAddr
getCarbonAddr cfg = do
    let host = (graphiteHost . graphiteConfig) cfg
    let port = (graphitePort . graphiteConfig) cfg
    -- addrInfos <- getAddrInfo (Just defaultHints)
    addrInfos <- getAddrInfo Nothing
                   (Just host)
                   (Just (show port))
    putStrLn $ "addrInfos: " ++ show addrInfos
    c <- case addrInfos of
           (addrInfo : _) -> return (addrAddress addrInfo)
           _ -> unsupportedAddressError host
    return c
  where
    unsupportedAddressError h = ioError $ userError $
      "unsupported address: " ++ h

主机和端口的配置值分别为“localhost”和2023。当我在升级到Yosemite后在我的OS X上运行它时 - 我看到以下崩溃：

addrInfos: [AddrInfo {addrFlags = [], addrFamily = AF_INET6, addrSocketType = Datagram, addrProtocol = 17, addrAddress = [::1]:2023, addrCanonName = Nothing},AddrInfo {addrFlags = [], addrFamily = AF_INET6, addrSocketType = Stream, addrProtocol = 6, addrAddress = [::1]:2023, addrCanonName = Nothing},AddrInfo {addrFlags = [], addrFamily = AF_INET, addrSocketType = Datagram, addrProtocol = 17, addrAddress = 127.0.0.1:2023, addrCanonName = Nothing},AddrInfo {addrFlags = [], addrFamily = AF_INET, addrSocketType = Stream, addrProtocol = 6, addrAddress = 127.0.0.1:2023, addrCanonName = Nothing},AddrInfo {addrFlags = [], addrFamily = AF_INET6, addrSocketType = Datagram, addrProtocol = 17, addrAddress = [fe80::1%lo0]:2023, addrCanonName = Nothing},AddrInfo {addrFlags = [], addrFamily = AF_INET6, addrSocketType = Stream, addrProtocol = 6, addrAddress = [fe80::1%lo0]:2023, addrCanonName = Nothing}]
LocalJob: connect: unsupported operation (Address family not supported by protocol family)

这对我来说似乎很奇怪，所以我决定运行这个C程序（google搜索“getaddrinfo”示例，更改主机名和端口，添加了ai_family的打印）：

#include <stdio.h>
#include <stdlib.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/socket.h>

#ifndef   NI_MAXHOST
#define   NI_MAXHOST 1025
#endif

int main(void)
{
    struct addrinfo *result;
    struct addrinfo *res;
    int error;

    /* resolve the domain name into a list of addresses */
    error = getaddrinfo("localhost", "2023", NULL, &result);
    if (error != 0)
    {
        fprintf(stderr, "error in getaddrinfo: %s\n", gai_strerror(error));
        return EXIT_FAILURE;
    }

    /* loop over all returned results and do inverse lookup */
    for (res = result; res != NULL; res = res->ai_next)
    {
        char hostname[NI_MAXHOST] = "";

        error = getnameinfo(res->ai_addr, res->ai_addrlen, hostname, NI_MAXHOST, NULL, 0, 0);
        if (error != 0)
        {
            fprintf(stderr, "error in getnameinfo: %s\n", gai_strerror(error));
            continue;
        }
        if (*hostname != '\0')
            printf("hostname: %s. ai_family: %i\n", hostname, res->ai_family);
    }

    freeaddrinfo(result);
    return EXIT_SUCCESS;
}

启动后，我看到了这个输出：

➜  getaddrinfotest  ./main
hostname: localhost. ai_family: 30
hostname: localhost. ai_family: 30
hostname: localhost. ai_family: 2
hostname: localhost. ai_family: 2
hostname: localhost. ai_family: 30
hostname: localhost. ai_family: 30

所以，ai_family 30似乎是一件奇怪的事情。据我所知socket.h sources，它是AF_TIPC协议，这是我以前从未听说过的一件非常罕见的事情。我还打开了haskell的packFamily' sources并且惊讶地看到它没有处理30的值（不知道AF_TIPC）。

我的问题是：现在最好的事情是什么？我是否正确地解决了问题？ haskell应该更好地处理未知的ai家庭吗？ //谢谢！

更新：我通过提示使用ipv4解决了一个问题：

addrInfos <- getAddrInfo (Just (defaultHints { addrFamily=AF_INET }))
               (Just host)
               (Just (show port))

但我仍然想知道如何以“正确的方式”解决这个问题。

Answer 1

默认情况下，getaddrinfo（及其Haskell绑定getAddrInfo）返回addrinfo的链接列表，该列表可以包含IPv4地址，IPv6地址或两者的混合。遗憾的是，套接字函数不允许将IPv4套接字连接到IPv6地址，因此当您遍历地址列表时，需要创建一个正确类型的套接字：

addrinfos <- getAddrInfo Nothing (Just hostname) (Just (show port))
let first = head addrinfos
sock <- socket (addrFamily first) Stream defaultProtocol
connect sock (addrAddress first)

注意(addrFamily first)如何传递给socket函数，以便在正确的协议族中创建套接字。

在实际代码中，您需要遍历列表addrinfos并尝试连接到getAddrInfo返回的所有地址。当您这样做时，不要忘记关闭连接失败的套接字。

Haskell：不支持的操作（协议族不支持地址族）

1 个答案: