IPv6 infrastructure support

Add autoconf rules to detect IPv6 availability and some of the neeeded
support functions. Add stubs for getaddrinfo and inet_ntop.
You can disable IPv6 at compile time with
./configure --without-ipv6

Signed-off-by: Karsten Keil <kkeil@suse.de>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

lib/getaddrinfo.c

@@ -0,0 +1,121 @@
+/*
+ * getaddrinfo.c
+ *
+ * Simple version of getaddrinfo()
+ *
+ */
+
+#include "config.h"
+
+extern int errno;
+extern int h_errno;
+
+void freeaddrinfo(struct addrinfo *res)
+{
+    if (!res)
+        return;
+    if (res->ai_next)
+        freeaddrinfo(res->ai_next);
+    if (res->ai_addr)
+        free(res->ai_addr);
+    if (res->ai_canonname)
+        free(res->ai_canonname);
+    free(res);
+}
+
+int getaddrinfo(const char *node, const char *service, const struct addrinfo *hints,
+                struct addrinfo **res)
+{
+    struct hostent  *host;
+    struct sockaddr *sa;
+    int err, size = 0;
+
+    if ((!node) || (!res)) {
+        errno = EINVAL;
+        return EAI_SYSTEM;
+    }
+    *res = NULL;
+    /* we do not support service in this version */
+    if (service) {
+        errno = EINVAL;
+        return EAI_SYSTEM;
+    }
+    host = gethostbyname(node);
+    if (!host)
+        return EAI_NONAME;
+    if (hints) {
+        if (hints->ai_family != AF_UNSPEC) {
+            if (hints->ai_family != host->h_addrtype)
+                return EAI_ADDRFAMILY;
+        }
+    }
+    *res =  malloc(sizeof(struct addrinfo));
+    if (!*res) {
+        return EAI_MEMORY;
+    }
+    memset(*res, 0, sizeof(struct addrinfo));
+    (*res)->ai_family = host->h_addrtype;
+    if (host->h_length) {
+        if (host->h_addrtype == AF_INET)
+            size = sizeof(struct sockaddr_in);
+#ifdef HAVE_IPV6
+        else if (host->h_addrtype == AF_INET6)
+            size = sizeof(struct sockaddr_in6);
+#endif
+        else {
+            free(*res);
+            *res = NULL;
+            return EAI_ADDRFAMILY;
+        }
+        sa = malloc(size);
+        if (!sa) {
+            free(*res);
+            *res = NULL;
+            return EAI_MEMORY;
+        }
+        memset(sa, 0, size);
+        (*res)->ai_addr = sa;
+        (*res)->ai_addrlen = size;
+        sa->sa_family = host->h_addrtype;
+        if (host->h_addrtype == AF_INET)
+            memcpy(&((struct sockaddr_in *)sa)->sin_addr, host->h_addr, host->h_length);
+#ifdef HAVE_IPV6
+        else
+            memcpy(&((struct sockaddr_in6 *)sa)->sin6_addr, host->h_addr, host->h_length);
+#endif
+    }
+    if (host->h_name)
+       (*res)->ai_canonname = strdup(host->h_name);
+
+    /* we only handle the first address entry and do not build a list now */
+    return 0;
+}
+
+
+
+const char *gai_strerror(int errcode)
+{
+    const char *s = NULL;
+
+    switch(errcode) {
+    case 0:
+        s = "no error";
+        break;
+    case EAI_MEMORY:
+        s = "no memory";
+        break;
+    case EAI_SYSTEM:
+        s = strerror(errno);
+        break;
+    case EAI_NONAME:
+        s = hstrerror(h_errno);
+        break;
+    case EAI_ADDRFAMILY:
+        s = "address does not match address family";
+        break;
+    default:
+        s = "unknown error code";
+        break;
+    }
+    return s;
+}