delayed acking

dnsd.c

@@ -42,6 +42,11 @@ char activepacket[4096];
 int outid;
 int outbuflen;
 char outbuf[64*1024];
+char delayed_q_name[256];
+short delayed_q_type;
+short delayed_q_id;
+struct sockaddr_in delayed_q_from;
+int delayed_q_fromlen;
 
 static int
 readname(char *packet, char *dst, char *src)
@@ -126,6 +131,9 @@ open_dnsd(const char *domain)
 	topdomain[sizeof(topdomain) - 1] = 0;
 
 	packetlen = 0;
+	delayed_q_type = 0;
+	delayed_q_id = 0;
+	delayed_q_fromlen = 0;
 
 	return fd;
 }
@@ -169,6 +177,12 @@ dnsd_haspacket()
 	return (outbuflen > 0);
 }
 
+int
+dnsd_hasack()
+{
+	return (delayed_q_id != 0);
+}
+
 void
 dnsd_queuepacket(const char *buf, const int buflen)
 {
@@ -179,7 +193,7 @@ dnsd_queuepacket(const char *buf, const int buflen)
 }
 
 static void
-dnsd_respond(int fd, char *name, short type, short id, struct sockaddr_in from)
+dnsd_send(int fd, char *name, short type, short id, struct sockaddr_in from)
 {
 	int len;
 	char *p;
@@ -229,6 +243,13 @@ dnsd_respond(int fd, char *name, short type, short id, struct sockaddr_in from)
 	outbuflen = 0;
 }
 
+void
+dnsd_forceack(int fd)
+{
+	dnsd_send(fd, delayed_q_name, delayed_q_type, delayed_q_id, delayed_q_from);
+	delayed_q_id = 0;
+}
+
 int
 dnsd_read(int fd, char *buf, int buflen)
 {
@@ -274,7 +295,16 @@ dnsd_read(int fd, char *buf, int buflen)
 				READSHORT(type, data);
 				READSHORT(class, data);
 				
-				dnsd_respond(fd, name, type, id, from);
+				if (dnsd_haspacket()) {
+					dnsd_send(fd, name, type, id, from);
+				} else {
+					// Store needed info about delayed response
+					strncpy(delayed_q_name, name, 256);
+					delayed_q_type = type;
+					delayed_q_id = id;
+					delayed_q_fromlen = addrlen;
+					memcpy((struct sockaddr*)&delayed_q_from, (struct sockaddr*)&from, addrlen);
+				}
 				
 				lastblock = name[0] - '0';
 				np = name;

dnsd.h

@@ -25,6 +25,8 @@ void close_dnsd(int);
 int dnsd_read(int, char *, int);
 
 int dnsd_haspacket();
+int dnsd_hasack();
+void dnsd_forceack(int);
 void dnsd_queuepacket(const char *, const int);
 
 

dnstund.c

@@ -53,8 +53,13 @@ tunnel(int tun_fd, int dns_fd)
 	frame = malloc(64*1024);
 	
 	while (running) {
-		tv.tv_sec = 1;
-		tv.tv_usec = 0;
+		if (dnsd_hasack()) {
+			tv.tv_sec = 0;
+			tv.tv_usec = 150000;
+		} else {
+			tv.tv_sec = 1;
+			tv.tv_usec = 0;
+		}
 
 		FD_ZERO(&fds);
 		if(!dnsd_haspacket()) 
@@ -88,6 +93,12 @@ tunnel(int tun_fd, int dns_fd)
 					write_tun(tun_fd, frame, read + 4);
 				}
 			} 
+		} else {
+			// Timeout on select()
+			if (dnsd_hasack()) {
+				printf("Got no data, sending delayed ACK\n");
+				dnsd_forceack(dns_fd);
+			}
 		}
 	}