Move resolution of client and upstream host names to a dedicated thread #405

DL6ER · 2018-10-25T17:58:02Z

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Move resolution of client and upstream host names to a dedicated thread. This PR fixes #404

This template was created based on the work of udemy-dl.

…ad. Fixes #404 Signed-off-by: DL6ER <dl6er@dl6er.de>

Signed-off-by: DL6ER <dl6er@dl6er.de>

AzureMarker · 2018-10-26T17:50:57Z

resolve.c

-// to account for new clients (and forward destinations)
-void resolveNewClients(void)
+// Resolve upstream destination host names
+static void resolveForwardDestinations(bool onlynew)


We have the capability to resolve all forward destinations instead of just new ones, but we don't use it currently. When all clients are re-resolved, we should also re-resolve forward destination names.

I wonder if this is really meaningful, as we don't expect the forward destination host names to ever change, do we? In contrast, users may decide to rename their local devices, e.g., from android-a479b97ef09880b890d233a to paul-iphone

Perhaps if the upstream is localhost, and the hostname changes? It may not be worth implementing, but on the other hand, it is a very small cost (usually only 1 to 3 upstreams).

AzureMarker · 2018-10-26T17:51:58Z

resolve.c

+void *resolver_thread(void *val)
+{
+	// Set thread name
+	prctl(PR_SET_NAME,"resolver",0,0,0);


This may get confused with DNS resolver.

It's only the thread name that is displayed, e.g., by htop. I don't think that anything can really get confused here:

To me, I see in that list the jobs of FTL listed out. It resolves domains on the resolver thread, does database stuff on the database thread, listens to sockets and telnet on their respective threads, and does some housekeeping on the housekeeper thread. I don't see any other thread that looks like "DNS" or "dnsmasq", so the resolver thread seems to be doing that job. A better name might be "internal resolver".

The thread name is limited to 16 characters (15 chars + 0x0), we can do:

another possibility might be DNS client

DNS client sounds fine.

… destinations Signed-off-by: DL6ER <dl6er@dl6er.de>

Signed-off-by: DL6ER <dl6er@dl6er.de>

AzureMarker · 2018-10-27T18:44:26Z

resolve.c

-	for(i = 0; i < counters.forwarded; i++)
+}
+
+pthread_t resolverthread;


Can this be moved to where the other threads are defined (main)?

They are all defined in dnsmasq_interface.c (close to where the threads are launched). I'll move the definition there.

Ah ya, sorry, thought that was main for a second (we used to launch the threads from there).

AzureMarker · 2018-10-27T18:46:12Z

dnsmasq_interface.c

+	// Start thread that will stay in the background until host names needs to be resolved
+	if(pthread_create( &resolverthread, &attr, resolver_thread, NULL ) != 0)
+	{
+		logg("Unable to open resolver thread. Exiting...");


As the thread was renamed to DNS client, rename this reference.

AzureMarker · 2018-10-27T18:46:51Z

FTL.h

@@ -279,3 +279,4 @@ extern pthread_t telnet_listenthreadv6;
 extern pthread_t socket_listenthread;
 extern pthread_t DBthread;
 extern pthread_t GCthread;
+extern pthread_t resolverthread;


As the thread was renamed to DNS client, rename this variable.

AzureMarker · 2018-10-27T18:47:38Z

resolve.c

+}
+
+pthread_t resolverthread;
+void *resolver_thread(void *val)


As the thread was renamed to DNS client, rename this function.

Signed-off-by: DL6ER <dl6er@dl6er.de>

resolve.c

AzureMarker · 2018-10-27T19:03:08Z

resolve.c

-		if(strlen(hostname) > 0)
+		// If onlynew flag is set, we will only resolve new clients
+		// If not, we will try to re-resolve all known clients
+		if(onlynew && clients[i].new)


If onlynew is false, no resolving will occur at all.

AzureMarker · 2018-10-27T19:03:18Z

resolve.c

-		if(clients[i].new)
+		// If onlynew flag is set, we will only resolve new upstream destinations
+		// If not, we will try to re-resolve all known upstream destinations
+		if(onlynew && forwarded[i].new)


See above comment.

Signed-off-by: DL6ER <dl6er@dl6er.de>

…T new, we skip this one. In all other cases, we try to resolve. Signed-off-by: DL6ER <dl6er@dl6er.de>

DL6ER added 2 commits October 25, 2018 19:53

Move resolution of client and upstream host names to a dedicated thre…

f2f3566

…ad. Fixes #404 Signed-off-by: DL6ER <dl6er@dl6er.de>

Remove obsolete debug output

f10b49c

Signed-off-by: DL6ER <dl6er@dl6er.de>

DL6ER added the Code maintanance label Oct 25, 2018

DL6ER added this to the v4.1 milestone Oct 25, 2018

DL6ER requested a review from AzureMarker October 25, 2018 17:58

AzureMarker suggested changes Oct 26, 2018

View reviewed changes

DL6ER added 2 commits October 26, 2018 20:17

Call to ">reresolve" also re-resolves host names of all known forward…

5135663

… destinations Signed-off-by: DL6ER <dl6er@dl6er.de>

Use "DNS client" as custom thread name for the new name resolving thread

1a3a595

Signed-off-by: DL6ER <dl6er@dl6er.de>

AzureMarker suggested changes Oct 27, 2018

View reviewed changes

Rename routines/variables to reflect "DNS client"

fd53505

Signed-off-by: DL6ER <dl6er@dl6er.de>

AzureMarker suggested changes Oct 27, 2018

View reviewed changes

DL6ER added 2 commits October 27, 2018 21:06

Also re-resolve upstream host names every hour

e6157da

Signed-off-by: DL6ER <dl6er@dl6er.de>

Change logic of onlynew variable: If onlynew is set and an item is NO…

9f86037

…T new, we skip this one. In all other cases, we try to resolve. Signed-off-by: DL6ER <dl6er@dl6er.de>

AzureMarker approved these changes Oct 27, 2018

View reviewed changes

AzureMarker merged commit 7b01d20 into development Oct 27, 2018

AzureMarker deleted the new/resolve_thread branch October 27, 2018 19:33

DL6ER mentioned this pull request Jun 29, 2020

Fix dnsmasq TCP worker buffer overflow #822

Merged

5 tasks

DL6ER mentioned this pull request Sep 18, 2020

Only resolve active clients #872

Merged

5 tasks

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Move resolution of client and upstream host names to a dedicated thread #405

Move resolution of client and upstream host names to a dedicated thread #405

DL6ER commented Oct 25, 2018

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Move resolution of client and upstream host names to a dedicated thread #405

Move resolution of client and upstream host names to a dedicated thread #405

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DL6ER commented Oct 25, 2018

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