Merge branch 'master' of github.com:DNSCrypt/dnscrypt-proxy

* 'master' of github.com:DNSCrypt/dnscrypt-proxy:
  Add jsdelivr as an alternative source URL
  Before probing HTTP/3, check a negative cache

Author: jedisct1

dnscrypt-proxy/example-dnscrypt-proxy.toml

@@ -769,6 +769,7 @@ format = 'tsv'
 urls = [
   'https://raw.githubusercontent.com/DNSCrypt/dnscrypt-resolvers/master/v3/public-resolvers.md',
   'https://download.dnscrypt.info/resolvers-list/v3/public-resolvers.md',
+  'https://cdn.jsdelivr.net/gh/DNSCrypt/dnscrypt-resolvers@master/v3/public-resolvers.md'
 ]
 cache_file = 'public-resolvers.md'
 minisign_key = 'RWQf6LRCGA9i53mlYecO4IzT51TGPpvWucNSCh1CBM0QTaLn73Y7GFO3'
@@ -781,6 +782,7 @@ prefix = ''
 urls = [
   'https://raw.githubusercontent.com/DNSCrypt/dnscrypt-resolvers/master/v3/relays.md',
   'https://download.dnscrypt.info/resolvers-list/v3/relays.md',
+  'https://cdn.jsdelivr.net/gh/DNSCrypt/dnscrypt-resolvers@master/v3/relays.md'
 ]
 cache_file = 'relays.md'
 minisign_key = 'RWQf6LRCGA9i53mlYecO4IzT51TGPpvWucNSCh1CBM0QTaLn73Y7GFO3'
@@ -790,13 +792,13 @@ prefix = ''
 ### ODoH (Oblivious DoH) servers and relays
 
 # [sources.odoh-servers]
-#   urls = ['https://raw.githubusercontent.com/DNSCrypt/dnscrypt-resolvers/master/v3/odoh-servers.md', 'https://download.dnscrypt.info/resolvers-list/v3/odoh-servers.md']
+#   urls = ['https://raw.githubusercontent.com/DNSCrypt/dnscrypt-resolvers/master/v3/odoh-servers.md', 'https://download.dnscrypt.info/resolvers-list/v3/odoh-servers.md', 'https://cdn.jsdelivr.net/gh/DNSCrypt/dnscrypt-resolvers@master/v3/odoh-servers.md']
 #   cache_file = 'odoh-servers.md'
 #   minisign_key = 'RWQf6LRCGA9i53mlYecO4IzT51TGPpvWucNSCh1CBM0QTaLn73Y7GFO3'
 #   refresh_delay = 73
 #   prefix = ''
 # [sources.odoh-relays]
-#   urls = ['https://raw.githubusercontent.com/DNSCrypt/dnscrypt-resolvers/master/v3/odoh-relays.md', 'https://download.dnscrypt.info/resolvers-list/v3/odoh-relays.md']
+#   urls = ['https://raw.githubusercontent.com/DNSCrypt/dnscrypt-resolvers/master/v3/odoh-relays.md', 'https://download.dnscrypt.info/resolvers-list/v3/odoh-relays.md', 'https://cdn.jsdelivr.net/gh/DNSCrypt/dnscrypt-resolvers@master/v3/odoh-relays.md']
 #   cache_file = 'odoh-relays.md'
 #   minisign_key = 'RWQf6LRCGA9i53mlYecO4IzT51TGPpvWucNSCh1CBM0QTaLn73Y7GFO3'
 #   refresh_delay = 73
@@ -814,7 +816,7 @@ prefix = ''
 ### This is a subset of the `public-resolvers` list, so enabling both is useless.
 
 # [sources.parental-control]
-#   urls = ['https://raw.githubusercontent.com/DNSCrypt/dnscrypt-resolvers/master/v3/parental-control.md', 'https://download.dnscrypt.info/resolvers-list/v3/parental-control.md']
+#   urls = ['https://raw.githubusercontent.com/DNSCrypt/dnscrypt-resolvers/master/v3/parental-control.md', 'https://download.dnscrypt.info/resolvers-list/v3/parental-control.md', 'https://cdn.jsdelivr.net/gh/DNSCrypt/dnscrypt-resolvers@master/v3/parental-control.md']
 #   cache_file = 'parental-control.md'
 #   minisign_key = 'RWQf6LRCGA9i53mlYecO4IzT51TGPpvWucNSCh1CBM0QTaLn73Y7GFO3'
 

dnscrypt-proxy/xtransport.go

@@ -653,10 +653,16 @@ func (xTransport *XTransport) Fetch(
 
 	if xTransport.h3Transport != nil {
 		if xTransport.http3Probe {
-			// Always try HTTP/3 first when http3_probe is enabled,
-			// without checking for Alt-Svc
-			client.Transport = xTransport.h3Transport
-			dlog.Debugf("Probing HTTP/3 transport for [%s]", url.Host)
+			xTransport.altSupport.RLock()
+			altPort, inNegativeCache := xTransport.altSupport.cache[url.Host]
+			inNegativeCache = inNegativeCache && altPort == 0
+			xTransport.altSupport.RUnlock()
+			if !inNegativeCache {
+				client.Transport = xTransport.h3Transport
+				dlog.Debugf("Probing HTTP/3 transport for [%s]", url.Host)
+			} else {
+				dlog.Debugf("Skipping HTTP/3 probe for [%s] - previously failed", url.Host)
+			}
 		} else {
 			// Otherwise use traditional Alt-Svc detection
 			xTransport.altSupport.RLock()