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, 12 insertions, 0 deletions

diff --git a/src/network/res_send.c b/src/network/res_send.c
new file mode 100644
index 00000000..19cfe0f6
--- /dev/null
+++ b/src/network/res_send.c
@@ -0,0 +1,12 @@
+#include <resolv.h>
+#include "libc.h"
+
+int __res_msend(int, const unsigned char *const *, const int *, unsigned char *const *, int *, int);
+
+int __res_send(const unsigned char *msg, int msglen, unsigned char *answer, int anslen)
+{
+	int r = __res_msend(1, &msg, &msglen, &answer, &anslen, anslen);
+	return r<0 ? r : anslen;
+}
+
+weak_alias(__res_send, res_send);