From 24c13cb8b2d8caf744a5369854da4d6f9f68945c Mon Sep 17 00:00:00 2001
From: Simon Rettberg
Date: Thu, 7 Mar 2019 22:38:28 +0100
Subject: [FUSE] Add --sticky mode to ignore alt-servers announced by servers

---
 src/fuse/connection.c | 10 +++++++---
 src/fuse/connection.h |  2 +-
 src/fuse/main.c       | 10 ++++++++--
 3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/src/fuse/connection.c b/src/fuse/connection.c
index 294983b..fc9f05b 100644
--- a/src/fuse/connection.c
+++ b/src/fuse/connection.c
@@ -31,6 +31,7 @@ static bool connectionInitDone = false;
 static bool threadInitDone = false;
 static pthread_mutex_t mutexInit = PTHREAD_MUTEX_INITIALIZER;
 static bool keepRunning = true;
+static bool learnNewServers;
 
 // List of pending requests
 static struct {
@@ -95,7 +96,7 @@ static bool throwDataAway(int sockFd, uint32_t amount);
 static void enqueueRequest(dnbd3_async_t *request);
 static dnbd3_async_t* removeRequest(dnbd3_async_t *request);
 
-bool connection_init(const char *hosts, const char *lowerImage, const uint16_t rid)
+bool connection_init(const char *hosts, const char *lowerImage, const uint16_t rid, const bool doLearnNew)
 {
 	int sock = -1;
 	char host[SHORTBUF];
@@ -114,6 +115,7 @@ bool connection_init(const char *hosts, const char *lowerImage, const uint16_t r
 		dnbd3_host_t tempHosts[MAX_HOSTS_PER_ADDRESS];
 		const char *current, *end;
 		int altIndex = 0;
+		learnNewServers = doLearnNew;
 		memset( altservers, 0, sizeof altservers );
 		connection.sockFd = -1;
 		current = hosts;
@@ -453,7 +455,9 @@ static void* connection_backgroundThread(void *something UNUSED)
 		const bool panic = connection.sockFd == -1;
 		// Check alt servers
 		if ( panic || timing_reachedPrecise( &nextRttCheck, &now ) ) {
-			addAltServers();
+			if ( learnNewServers ) {
+				addAltServers();
+			}
 			sortAltServers();
 			probeAltServers();
 			if ( panic || timing_diff( &connection.startupTime, &now ) <= STARTUP_MODE_DURATION ) {
@@ -853,7 +857,7 @@ static void switchConnection(int sockFd, alt_server_t *srv)
  */
 static void requestAltServers()
 {
-	if ( connection.sockFd == -1 )
+	if ( connection.sockFd == -1 || !learnNewServers )
 		return;
 	dnbd3_request_t request = { 0 };
 	request.magic = dnbd3_packet_magic;
diff --git a/src/fuse/connection.h b/src/fuse/connection.h
index c919d95..cae554c 100644
--- a/src/fuse/connection.h
+++ b/src/fuse/connection.h
@@ -20,7 +20,7 @@ typedef struct _dnbd3_async {
 	bool success;      // Will be set to true if the request succeeded
 } dnbd3_async_t;
 
-bool connection_init(const char *hosts, const char *image, const uint16_t rid);
+bool connection_init(const char *hosts, const char *image, const uint16_t rid, const bool learnNewServers);
 
 bool connection_initThreads();
 
diff --git a/src/fuse/main.c b/src/fuse/main.c
index e1b2633..1a5643c 100644
--- a/src/fuse/main.c
+++ b/src/fuse/main.c
@@ -277,11 +277,12 @@ static void printUsage(char *argv0, int exitCode)
 	printf( "   -l --log        Write log to given location\n" );
 	printf( "   -o --option     Mount options to pass to libfuse\n" );
 	printf( "   -r --rid        Revision to use (omit or pass 0 for latest)\n" );
+	printf( "   -S --sticky     Use only servers from command line (no learning from servers)\n" );
 	printf( "   -s              Single threaded mode\n" );
 	exit( exitCode );
 }
 
-static const char *optString = "dfHh:i:l:o:r:sVv";
+static const char *optString = "dfHh:i:l:o:r:SsVv";
 static const struct option longOpts[] = {
         { "debug", no_argument, NULL, 'd' },
         { "help", no_argument, NULL, 'H' },
@@ -290,6 +291,7 @@ static const struct option longOpts[] = {
         { "log", required_argument, NULL, 'l' },
         { "option", required_argument, NULL, 'o' },
         { "rid", required_argument, NULL, 'r' },
+        { "sticky", no_argument, NULL, 'S' },
         { "version", no_argument, NULL, 'v' },
         { 0, 0, 0, 0 }
 };
@@ -303,6 +305,7 @@ int main(int argc, char *argv[])
 	char **newArgv;
 	int newArgc;
 	int opt, lidx;
+	bool learnNewServers = true;
 
 	if ( argc <= 1 || strcmp( argv[1], "--help" ) == 0 || strcmp( argv[1], "--usage" ) == 0 ) {
 		printUsage( argv[0], 0 );
@@ -358,6 +361,9 @@ int main(int argc, char *argv[])
 		case 's':
 			newArgv[newArgc++] = "-s";
 			break;
+		case 'S':
+			learnNewServers = false;
+			break;
 		case 'f':
 			newArgv[newArgc++] = "-f";
 			break;
@@ -380,7 +386,7 @@ int main(int argc, char *argv[])
 		}
 	}
 
-	if ( !connection_init( server_address, image_Name, rid ) ) {
+	if ( !connection_init( server_address, image_Name, rid, learnNewServers ) ) {
 		logadd( LOG_ERROR, "Could not connect to any server. Bye.\n" );
 		return EXIT_FAILURE;
 	}
-- 
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