From 5b5ac2317e047dd77bf96a171a5e236973606a83 Mon Sep 17 00:00:00 2001
From: Jonathan McDowell <noodles@earth.li>
Date: Wed, 9 Oct 2013 11:46:42 +0100
Subject: [PATCH] Switch keyd to allow multiple clients to be served at once

keyd was only accepting a single connection at a time and dealing with
all the requests from it before accepting the next client. This causes
delays in regular HKP processing while running something like wotsap on
a live keyserver.

Most of the pieces were already in place to deal with a per request select
based processing loop, so this commit switches to that model. A better
solution in the future may be to consider the use of libevent or libev,
but at present this enables the use of long runs stats programs while
still being able to service HKP requests in reasonable time.
---
 keyd.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 52 insertions(+), 9 deletions(-)

diff --git a/keyd.c b/keyd.c
index e43115d..4528c96 100644
--- a/keyd.c
+++ b/keyd.c
@@ -43,6 +43,9 @@
 #include "parsekey.h"
 #include "version.h"
 
+/* Maximum number of clients we're prepared to accept at once */
+#define MAX_CLIENTS 16
+
 static struct keyd_stats *stats;
 
 void daemonize(void)
@@ -124,7 +127,7 @@ int sock_init(const char *sockname)
 
 	fd = socket(PF_UNIX, SOCK_STREAM, 0);
 	if (fd != -1) {
-		ret = fcntl(fd, F_SETFD, 1);
+		ret = fcntl(fd, F_SETFD, FD_CLOEXEC);
 	}
 
 	if (ret != -1) {
@@ -445,16 +448,14 @@ int sock_accept(int fd)
 	socklen = sizeof(sock);
 	srv = accept(fd, (struct sockaddr *) &sock, &socklen);
 	if (srv != -1) {
-		ret = fcntl(srv, F_SETFD, 1);
+		ret = fcntl(srv, F_SETFD, FD_CLOEXEC);
 	}
 
 	if (ret != -1) {
 		stats->connects++;
-		while (!sock_do(srv)) ;
-		sock_close(srv);
 	}
 
-	return 1;
+	return (srv);
 }
 
 static void usage(void)
@@ -472,7 +473,7 @@ static void usage(void)
 
 int main(int argc, char *argv[])
 {
-	int fd = -1;
+	int fd = -1, maxfd, i, clients[MAX_CLIENTS];
 	fd_set rfds;
 	char sockname[1024];
 	char *configfile = NULL;
@@ -522,14 +523,56 @@ int main(int argc, char *argv[])
 	if (fd != -1) {
 		FD_ZERO(&rfds);
 		FD_SET(fd, &rfds);
+		maxfd = fd;
+		memset(clients, -1, sizeof (clients));
 
 		config.dbbackend->initdb(false);
 
 		logthing(LOGTHING_NOTICE, "Accepting connections.");
-		while (!cleanup() && select(fd + 1, &rfds, NULL, NULL, NULL) != -1) {
-			logthing(LOGTHING_INFO, "Accepted connection.");
-			sock_accept(fd);
+		while (!cleanup() && select(maxfd + 1, &rfds, NULL, NULL, NULL) != -1) {
+			/*
+			 * Deal with existing clients first; if we're at our
+			 * connection limit then processing them might free
+			 * things up and let us accept the next client below.
+			 */
+			for (i = 0; i < MAX_CLIENTS; i++) {
+				if (clients[i] != -1 &&
+						FD_ISSET(clients[i], &rfds)) {
+					logthing(LOGTHING_DEBUG,
+						"Handling connection for client %d.", i);
+					if (sock_do(clients[i])) {
+						sock_close(clients[i]);
+						clients[i] = -1;
+						logthing(LOGTHING_DEBUG,
+							"Closed connection for client %d.", i);
+					}
+				}
+			}
+			/*
+			 * Check if we have a new incoming connection to accept.
+			 */
+			if (FD_ISSET(fd, &rfds)) {
+				for (i = 0; i < MAX_CLIENTS; i++) {
+					if (clients[i] == -1) {
+						break;
+					}
+				}
+				if (i < MAX_CLIENTS) {
+					logthing(LOGTHING_INFO,
+						"Accepted connection %d.", i);
+					clients[i] = sock_accept(fd);
+				}
+			}
+			FD_ZERO(&rfds);
 			FD_SET(fd, &rfds);
+			maxfd = fd;
+			for (i = 0; i < MAX_CLIENTS; i++) {
+				if (clients[i] != -1) {
+					FD_SET(clients[i], &rfds);
+					maxfd = (maxfd > clients[i]) ?
+							maxfd : clients[i];
+				}
+			}
 		}
 		config.dbbackend->cleanupdb();
 		sock_close(fd);
-- 
2.39.2