make inet_ntop format v4-mapped ipv6 addresses properly

based on a patch by orc. POSIX actually fails to specify the format of
the ntop conversion; presumably, any output that will correctly
round-trip back via the (well-specified) pton operation is acceptable.
the new behavior is much more convenient than the old, however.

this patch also affects getnameinfo, which is implemented in terms of
inet_ntop and which is the preferred interface for performing this
conversion.

I've also removed some inexplicable cruft (filling the buffer with 'x'
before doing anything) whose origin I was unable to track down.

diff --git a/src/network/inet_ntop.c b/src/network/inet_ntop.c
index 76ae556..e9e2823 100644 (file)
--- a/src/network/inet_ntop.c
+++ b/src/network/inet_ntop.c
@@ -18,14 +18,20 @@ const char *inet_ntop(int af, const void *restrict a0, char *restrict s, socklen
                        return s;
                break;
        case AF_INET6:
-               memset(buf, 'x', sizeof buf);
-               buf[sizeof buf-1]=0;
-               snprintf(buf, sizeof buf,
-                       "%x:%x:%x:%x:%x:%x:%x:%x",
-                       256*a[0]+a[1],256*a[2]+a[3],
-                       256*a[4]+a[5],256*a[6]+a[7],
-                       256*a[8]+a[9],256*a[10]+a[11],
-                       256*a[12]+a[13],256*a[14]+a[15]);
+               if (memcmp(a, "\0\0\0\0\0\0\0\0\0\0\377\377", 12))
+                       snprintf(buf, sizeof buf,
+                               "%x:%x:%x:%x:%x:%x:%x:%x",
+                               256*a[0]+a[1],256*a[2]+a[3],
+                               256*a[4]+a[5],256*a[6]+a[7],
+                               256*a[8]+a[9],256*a[10]+a[11],
+                               256*a[12]+a[13],256*a[14]+a[15]);
+               else
+                       snprintf(buf, sizeof buf,
+                               "%x:%x:%x:%x:%x:%x:%d.%d.%d.%d",
+                               256*a[0]+a[1],256*a[2]+a[3],
+                               256*a[4]+a[5],256*a[6]+a[7],
+                               256*a[8]+a[9],256*a[10]+a[11],
+                               a[12],a[13],a[14],a[15]);
                /* Replace longest /(^0|:)[:0]{2,}/ with "::" */
                for (i=best=0, max=2; buf[i]; i++) {
                        if (i && buf[i] != ':') continue;