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, 14 insertions, 0 deletions

diff --git a/src/network/res_querydomain.c b/src/network/res_querydomain.c
new file mode 100644
index 00000000..c746dbe6
--- /dev/null
+++ b/src/network/res_querydomain.c
@@ -0,0 +1,14 @@
+#include <resolv.h>
+#include <string.h>
+
+int res_querydomain(const char *name, const char *domain, int class, int type, unsigned char *dest, int len)
+{
+	char tmp[256];
+	size_t nl = strnlen(name, 256);
+	size_t dl = strnlen(domain, 256);
+	if (nl+dl+1 > 255) return -1;
+	memcpy(tmp, name, nl);
+	tmp[nl] = '.';
+	memcpy(tmp+nl+1, domain, dl+1);
+	return res_query(tmp, class, type, dest, len);
+}