On 16/04/2012 18:32, Rich Felker wrote:
On Mon, Apr 16, 2012 at 05:57:47PM +0100, Ed W wrote:
Rich, disregarding posix for a moment, what does glibc do? Options
are: canonname=NULL or IP as string?
If the AI_CANONNAME flag is not specified, the value of the
ai_canonname field in the returned structure is unspecified; in this
case it should not be filled in at all unless there's no cost to
filling it (IIRC musl always fills it because filling it is free if
done right).
At present uclibc is returning the reverse dns lookup or textual IP
format. It should be trivial for me to supply a patch to make this
whatever we want - can someone define what we want? (Posix or
emulate some other wierdness?)
Per POSIX:
If nodename is not null, and if requested by the AI_CANONNAME
flag, the ai_canonname field of the first returned addrinfo
structure shall point to a null-terminated string containing the
canonical name corresponding to the input nodename; if the
canonical name is not available, then ai_canonname shall refer to
the nodename argument or a string with the same contents. The
contents of the ai_flags field of the returned structures are
undefined.
My reading is that in the numeric case, since there is no canonical
name, the text about storing a pointer to the input nodename, or a
duplicate of the same, applies.
OK, please see attached version 2 of my patch which I believe implements
this satisfactorarily
As before the motivation is to avoid making DNS queries when calling
getaddrinfo with a numerical IP address. Performance improves
dramatically in such situations
Grateful if others with more experience will verify and commit
Thanks
Ed W
Posix says that canonname should use the text representation of an IP address
when a numerical nodename given
See: http://pubs.opengroup.org/onlinepubs/9699919799/functions/getaddrinfo.html
Signed-off-by: Ed Wildgoose <[email protected]>
---
--- libc/inet/getaddrinfo.c.orig 2012-04-16 18:28:05.000000000 +0100
+++ libc/inet/getaddrinfo.c 2012-04-16 22:51:58.000000000 +0100
@@ -628,13 +628,20 @@
char
buffer[sizeof("ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255")];
while (at2 != NULL) {
- if (req->ai_flags & AI_CANONNAME) {
+ c = inet_ntop(at2->family, at2->addr, buffer,
sizeof(buffer));
+ if (c) {
+ namelen = strlen(c) + 1;
+ } else if (req->ai_flags & AI_CANONNAME) {
struct hostent *h = NULL;
int herrno;
struct hostent th;
size_t tmpbuflen = 512;
char *tmpbuf;
+ /* Hint says numeric, but address is not */
+ if (req->ai_flags & AI_NUMERICSERV)
+ return -EAI_NONAME;
+
do {
tmpbuflen *= 2;
tmpbuf = alloca(tmpbuflen);
@@ -656,9 +663,7 @@
return -EAI_SYSTEM;
}
- if (h == NULL)
- c = inet_ntop(at2->family, at2->addr,
buffer, sizeof(buffer));
- else
+ if (h != NULL)
c = h->h_name;
if (c == NULL)
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