implement new dns backend, res_send and other legacy resolver functions

this is the second phase of the "resolver overhaul" project.

the key additions in this commit are the __res_msend and __res_mkquery
functions, which have been factored so as to provide a backend for
both the legacy res_* functions and the standard getaddrinfo and
getnameinfo functions. the latter however are still using the old
backend code; there is code duplication which still needs to be
removed, and this will be the next phase of the resolver overhaul.

__res_msend is derived from the old __dns_doqueries function, but
generalized to send arbitrary caller-provided packets in parallel
rather than producing the parallel queries itself. this allows it to
be used (completely trivially) as a backend for res_send. the
factored-out query generation code, with slightly more generality, is
now part of __res_mkquery.

1 files changed, 10 insertions, 18 deletions

diff --git a/src/network/res_query.c b/src/network/res_query.c
index 3847da37..2b4e4bb1 100644
--- a/src/network/res_query.c
+++ b/src/network/res_query.c
@@ -1,25 +1,17 @@
-#define _GNU_SOURCE
 #include <resolv.h>
 #include <netdb.h>
-#include "__dns.h"
 #include "libc.h"
 
-int res_query(const char *name, int class, int type, unsigned char *dest, int len)
+int __res_mkquery(int, const char *, int, int, const unsigned char *, int, const unsigned char*, unsigned char *, int);
+int __res_send(const unsigned char *, int, unsigned char *, int);
+
+int __res_query(const char *name, int class, int type, unsigned char *dest, int len)
 {
-	if (class != 1 || len < 512)
-		return -1;
-	switch(__dns_doqueries(dest, name, &type, 1)) {
-	case EAI_NONAME:
-		h_errno = HOST_NOT_FOUND;
-		return -1;
-	case EAI_AGAIN:
-		h_errno = TRY_AGAIN;
-		return -1;
-	case EAI_FAIL:
-		h_errno = NO_RECOVERY;
-		return -1;
-	}
-	return 512;
+	unsigned char q[280];
+	int ql = __res_mkquery(0, name, class, type, 0, 0, 0, q, sizeof q);
+	if (ql < 0) return ql;
+	return __res_send(q, ql, dest, len);
 }
 
-weak_alias(res_query, res_search);
+weak_alias(__res_query, res_query);
+weak_alias(__res_query, res_search);