first draft

formating

Co-authored-by: Viktor Szakats <vszakats@users.noreply.github.com>

Update lib/url.c

Co-authored-by: Viktor Szakats <vszakats@users.noreply.github.com>

Update docs/libcurl/opts/CURLOPT_ALTSVC_CTRL.md

Co-authored-by: Daniel Stenberg <daniel@haxx.se>

docs/libcurl/opts/CURLOPT_ALTSVC_CTRL.md

@@ -26,6 +26,7 @@ CURLOPT_ALTSVC_CTRL - control alt-svc behavior
 #define CURLALTSVC_H1           (1L<<3)
 #define CURLALTSVC_H2           (1L<<4)
 #define CURLALTSVC_H3           (1L<<5)
+#define CURLALTSVC_NO_RETRY     (1L<<6)
 
 CURLcode curl_easy_setopt(CURL *handle, CURLOPT_ALTSVC_CTRL, long bitmask);
 ~~~
@@ -51,6 +52,11 @@ versions.
 
 Setting any bit enables the alt-svc engine.
 
+If the connection fails when trying to connect to an alternative host,
+the hostname from the URL is attempted instead.
+
+Failed connection problems that trigger this fallback include: ...
+
 ## CURLALTSVC_READONLYFILE
 
 Do not write the alt-svc cache back to the file specified with

docs/libcurl/symbols-in-versions

@@ -199,6 +199,7 @@ CURLALTSVC_H1                   7.64.1
 CURLALTSVC_H2                   7.64.1
 CURLALTSVC_H3                   7.64.1
 CURLALTSVC_READONLYFILE         7.64.1
+CURLALTSVC_NO_RETRY             8.14.0
 CURLAUTH_ANY                    7.10.6
 CURLAUTH_ANYSAFE                7.10.6
 CURLAUTH_AWS_SIGV4              7.75.0

include/curl/curl.h

@@ -1032,6 +1032,7 @@ typedef enum {
 #define CURLALTSVC_H1           (1L<<3)
 #define CURLALTSVC_H2           (1L<<4)
 #define CURLALTSVC_H3           (1L<<5)
+#define CURLALTSVC_NO_RETRY     (1L<<6)
 
 /* bitmask values for CURLOPT_UPLOAD_FLAGS */
 #define CURLULFLAG_ANSWERED (1L<<0)

lib/url.c

@@ -3426,7 +3426,9 @@ static void conn_meta_freeentry(void *p)
 
 static CURLcode create_conn(struct Curl_easy *data,
                             struct connectdata **in_connect,
-                            bool *reusedp)
+                            bool *reusedp,
+                            bool *async,
+                            bool *use_slist)
 {
   CURLcode result = CURLE_OK;
   struct connectdata *conn;
@@ -3537,9 +3539,12 @@ static CURLcode create_conn(struct Curl_easy *data,
    * Process the "connect to" linked list of hostname/port mappings.
    * Do this after the remote port number has been fixed in the URL.
    *************************************************************/
-  result = parse_connect_to_slist(data, conn, data->set.connect_to);
-  if(result)
-    goto out;
+  if(*use_slist) {
+    *use_slist = FALSE; /* next retry without slist */
+    result = parse_connect_to_slist(data, conn, data->set.connect_to);
+    if(result)
+      goto out;
+  }
 
   /*************************************************************
    * IDN-convert the proxy hostnames
@@ -3851,7 +3856,11 @@ CURLcode Curl_connect(struct Curl_easy *data,
 {
   CURLcode result;
   struct connectdata *conn;
+<<<<<<< HEAD
   bool reused = FALSE;
+=======
+  bool use_slist = TRUE; /* start by attempting to use the slist */
+>>>>>>> 3edfc1476 (first draft)
 
   *asyncp = FALSE; /* assume synchronous resolves by default */
   *protocol_done = FALSE;
@@ -3860,12 +3869,32 @@ CURLcode Curl_connect(struct Curl_easy *data,
   Curl_req_hard_reset(&data->req, data);
 
   /* call the stuff that needs to be called */
+<<<<<<< HEAD
   result = create_conn(data, &conn, &reused);
 
   if(result == CURLE_NO_CONNECTION_AVAILABLE) {
     DEBUGASSERT(!conn);
     return result;
   }
+=======
+  result = create_conn(data, &conn, asyncp, &use_slist);
+
+#ifndef CURL_DISABLE_ALTSVC
+  /* if we failed because of the avc cache retry */
+  if(result && data-> asi
+    && !use_slist
+    && !(data-> asi-> flags & CURLALTSVC_NO_RETRY)
+    ) {
+    if(conn && result != CURLE_NO_CONNECTION_AVAILABLE) {
+      Curl_detach_connection(data);
+      Curl_conn_terminate(data, conn, TRUE);
+    }
+
+    Curl_req_hard_reset(&data->req, data);
+    result = create_conn(data, &conn, asyncp, &use_slist);
+  }
+#endif
+>>>>>>> 3edfc1476 (first draft)
 
   if(!result) {
     DEBUGASSERT(conn);

tests/data/Makefile.am

@@ -280,5 +280,7 @@ test3100 test3101 test3102 test3103 test3104 test3105 \
 test3200 test3201 test3202 test3203 test3204 test3205 test3207 test3208 \
 test3209 test3210 test3211 test3212 test3213 test3214 test3215 \
 test4000 test4001
+test3209 test3210 test3211 test3212 test3213 test3214 \
+test3300
 
 EXTRA_DIST = $(TESTCASES) DISABLED

tests/data/test3300

@@ -0,0 +1,63 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP GET
+Alt-Svc
+onion
+</keywords>
+</info>
+
+#
+# Server-side
+<reply>
+<data>
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+Funny-head: yesyes
+
+-foo-
+</data>
+</reply>
+
+#
+# Client-side
+<client>
+<features>
+alt-svc
+Debug
+</features>
+<server>
+http
+</server>
+<name>
+alt-svc using to an onion server
+</name>
+<setenv>
+# make debug-curl accept Alt-Svc over plain HTTP
+CURL_ALTSVC_HTTP="yeah"
+</setenv>
+<command>
+--alt-svc "%LOGDIR/altsvc-%TESTNUMBER" "http://%HOSTIP:%HTTPPORT/%TESTNUMBER"
+</command>
+<file name="%LOGDIR/altsvc-%TESTNUMBER">
+h1 %HOSTIP %HTTPPORT h1 bad.onion %HTTPPORT "20290222 22:19:28" 0 0
+</file>
+
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<protocol>
+GET /%TESTNUMBER HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+User-Agent: curl/%VERSION
+Accept: */*
+
+</protocol>
+</verify>
+</testcase>