Initial pass at async resolving. This is ugly and leaks memory and I hate it, so dedicated thread incoming.

adsbus/resolve.c

@@ -0,0 +1,77 @@
+#define _GNU_SOURCE
+
+#include <assert.h>
+#include <fcntl.h>
+#include <netdb.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "peer.h"
+
+#include "resolve.h"
+
+struct resolve {
+	struct peer peer;
+
+	struct addrinfo **addrs;
+	const char **error;
+
+	struct peer *inner_peer;
+
+	struct addrinfo ar_request;
+	struct gaicb gaicb;
+	struct gaicb *requests[1];
+
+	struct sigevent sev;
+};
+
+static void resolve_handler(struct peer *peer) {
+	struct resolve *res = (struct resolve *) peer;
+
+	assert(!close(res->peer.fd));
+
+	int err = gai_error(&res->gaicb);
+	if (err == 0) {
+		*res->addrs = res->gaicb.ar_result;
+		*res->error = NULL;
+	} else {
+		*res->addrs = NULL;
+		*res->error = gai_strerror(err);
+	}
+	struct peer *inner_peer = res->inner_peer;
+	free(res);
+	inner_peer->event_handler(inner_peer);
+}
+
+static void resolve_callback(union sigval val) {
+	assert(!close(val.sival_int));
+}
+
+void resolve(struct peer *peer, const char *node, const char *service, int flags, struct addrinfo **addrs, const char **error) {
+	struct resolve *res = malloc(sizeof(*res));
+	res->addrs = addrs;
+	res->error = error;
+	res->inner_peer = peer;
+
+	int fds[2];
+	assert(!pipe2(fds, O_NONBLOCK));
+	res->peer.fd = fds[0];
+	res->peer.event_handler = resolve_handler;
+	peer_epoll_add((struct peer *) res, EPOLLRDHUP);
+
+	res->requests[0] = &res->gaicb;
+	res->gaicb.ar_name = node;
+	res->gaicb.ar_service = service;
+	res->gaicb.ar_request = &res->ar_request;
+	res->ar_request.ai_family = AF_UNSPEC;
+	res->ar_request.ai_socktype = SOCK_STREAM;
+	res->ar_request.ai_protocol = 0;
+	res->ar_request.ai_flags = AI_V4MAPPED | AI_ADDRCONFIG | flags;
+
+	res->sev.sigev_notify = SIGEV_THREAD;
+	res->sev.sigev_value.sival_int = fds[1];
+	res->sev.sigev_notify_function = resolve_callback;
+	res->sev.sigev_notify_attributes = NULL;
+
+	assert(!getaddrinfo_a(GAI_NOWAIT, res->requests, 1, &res->sev));
+}