alt-svc: add protocol version selection masking

So that users can mask in/out specific HTTP versions when Alt-Svc is
used.

 - Removed "h2c" and updated test case accordingly
 - Changed how the altsvc struct is laid out
 - Added ifdefs to make the unittest run even in a quiche-tree

Closes #4201

3 files changed, 65 insertions, 60 deletions

diff --git a/lib/altsvc.c b/lib/altsvc.c
index b20ec13ae..abea66c69 100644
--- a/lib/altsvc.c
+++ b/lib/altsvc.c
@@ -54,9 +54,7 @@ static enum alpnid alpn2alpnid(char *name)
     return ALPN_h1;
   if(strcasecompare(name, "h2"))
     return ALPN_h2;
-  if(strcasecompare(name, "h2c"))
-    return ALPN_h2c;
-#ifdef USE_QUICHE
+#if defined(USE_QUICHE) && !defined(UNITTESTS)
   if(strcasecompare(name, "h3-22"))
     return ALPN_h3;
 #else
@@ -74,10 +72,8 @@ const char *Curl_alpnid2str(enum alpnid id)
     return "h1";
   case ALPN_h2:
     return "h2";
-  case ALPN_h2c:
-    return "h2c";
   case ALPN_h3:
-#ifdef USE_QUICHE
+#if defined(USE_QUICHE) && !defined(UNITTESTS)
     return "h3-22";
 #else
     return "h3";
@@ -90,8 +86,8 @@ const char *Curl_alpnid2str(enum alpnid id)
 
 static void altsvc_free(struct altsvc *as)
 {
-  free(as->srchost);
-  free(as->dsthost);
+  free(as->src.host);
+  free(as->dst.host);
   free(as);
 }
 
@@ -106,17 +102,17 @@ static struct altsvc *altsvc_createid(const char *srchost,
   if(!as)
     return NULL;
 
-  as->srchost = strdup(srchost);
-  if(!as->srchost)
+  as->src.host = strdup(srchost);
+  if(!as->src.host)
     goto error;
-  as->dsthost = strdup(dsthost);
-  if(!as->dsthost)
+  as->dst.host = strdup(dsthost);
+  if(!as->dst.host)
     goto error;
 
-  as->srcalpnid = srcalpnid;
-  as->dstalpnid = dstalpnid;
-  as->srcport = curlx_ultous(srcport);
-  as->dstport = curlx_ultous(dstport);
+  as->src.alpnid = srcalpnid;
+  as->dst.alpnid = dstalpnid;
+  as->src.port = curlx_ultous(srcport);
+  as->dst.port = curlx_ultous(dstport);
 
   return as;
   error:
@@ -235,8 +231,8 @@ static CURLcode altsvc_out(struct altsvc *as, FILE *fp)
           "\"%d%02d%02d "
           "%02d:%02d:%02d\" "
           "%u %d\n",
-          Curl_alpnid2str(as->srcalpnid), as->srchost, as->srcport,
-          Curl_alpnid2str(as->dstalpnid), as->dsthost, as->dstport,
+          Curl_alpnid2str(as->src.alpnid), as->src.host, as->src.port,
+          Curl_alpnid2str(as->dst.alpnid), as->dst.host, as->dst.port,
           stamp.tm_year + 1900, stamp.tm_mon + 1, stamp.tm_mday,
           stamp.tm_hour, stamp.tm_min, stamp.tm_sec,
           as->persist, as->prio);
@@ -261,7 +257,7 @@ struct altsvcinfo *Curl_altsvc_init(void)
 #ifdef USE_NGHTTP2
     | CURLALTSVC_H2
 #endif
-#ifdef USE_HTTP3
+#ifdef ENABLE_QUIC
     | CURLALTSVC_H3
 #endif
     ;
@@ -374,9 +370,9 @@ static void altsvc_flush(struct altsvcinfo *asi, enum alpnid srcalpnid,
   for(e = asi->list.head; e; e = n) {
     struct altsvc *as = e->ptr;
     n = e->next;
-    if((srcalpnid == as->srcalpnid) &&
-       (srcport == as->srcport) &&
-       strcasecompare(srchost, as->srchost)) {
+    if((srcalpnid == as->src.alpnid) &&
+       (srcport == as->src.port) &&
+       strcasecompare(srchost, as->src.host)) {
       Curl_llist_remove(&asi->list, e, NULL);
       altsvc_free(as);
       asi->num--;
@@ -544,15 +540,15 @@ CURLcode Curl_altsvc_parse(struct Curl_easy *data,
 bool Curl_altsvc_lookup(struct altsvcinfo *asi,
                         enum alpnid srcalpnid, const char *srchost,
                         int srcport,
-                        enum alpnid *dstalpnid, const char **dsthost,
-                        int *dstport)
+                        struct altsvc **dstentry,
+                        const int versions) /* one or more bits */
 {
   struct curl_llist_element *e;
   struct curl_llist_element *n;
   time_t now = time(NULL);
   DEBUGASSERT(asi);
   DEBUGASSERT(srchost);
-  DEBUGASSERT(dsthost);
+  DEBUGASSERT(dstentry);
 
   for(e = asi->list.head; e; e = n) {
     struct altsvc *as = e->ptr;
@@ -563,13 +559,12 @@ bool Curl_altsvc_lookup(struct altsvcinfo *asi,
       altsvc_free(as);
       continue;
     }
-    if((as->srcalpnid == srcalpnid) &&
-       strcasecompare(as->srchost, srchost) &&
-       as->srcport == srcport) {
+    if((as->src.alpnid == srcalpnid) &&
+       strcasecompare(as->src.host, srchost) &&
+       (as->src.port == srcport) &&
+       (versions & as->dst.alpnid)) {
       /* match */
-      *dstalpnid = as->dstalpnid;
-      *dsthost = as->dsthost;
-      *dstport = as->dstport;
+      *dstentry = as;
       return TRUE;
     }
   }
diff --git a/lib/altsvc.h b/lib/altsvc.h
index eefb45bf6..99d0499af 100644
--- a/lib/altsvc.h
+++ b/lib/altsvc.h
@@ -28,20 +28,21 @@
 #include "llist.h"
 
 enum alpnid {
-  ALPN_none,
-  ALPN_h1,
-  ALPN_h2,
-  ALPN_h2c,
-  ALPN_h3
+  ALPN_none = 0,
+  ALPN_h1 = CURLALTSVC_H1,
+  ALPN_h2 = CURLALTSVC_H2,
+  ALPN_h3 = CURLALTSVC_H3
+};
+
+struct althost {
+  char *host;
+  unsigned short port;
+  enum alpnid alpnid;
 };
 
 struct altsvc {
-  char *srchost;
-  char *dsthost;
-  unsigned short srcport;
-  unsigned short dstport;
-  enum alpnid srcalpnid;
-  enum alpnid dstalpnid;
+  struct althost src;
+  struct althost dst;
   time_t expires;
   bool persist;
   int prio;
@@ -68,8 +69,8 @@ CURLcode Curl_altsvc_parse(struct Curl_easy *data,
 bool Curl_altsvc_lookup(struct altsvcinfo *asi,
                         enum alpnid srcalpnid, const char *srchost,
                         int srcport,
-                        enum alpnid *dstalpnid, const char **dsthost,
-                        int *dstport);
+                        struct altsvc **dstentry,
+                        int versions); /* one or more CURLALTSVC_H* bits */
 #else
 /* disabled */
 #define Curl_altsvc_save(a,b)
diff --git a/lib/url.c b/lib/url.c
index 0b681803d..30263258f 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -3158,42 +3158,51 @@ static CURLcode parse_connect_to_slist(struct Curl_easy *data,
   if(data->asi && !host && (port == -1) &&
      (conn->handler->protocol == CURLPROTO_HTTPS)) {
     /* no connect_to match, try alt-svc! */
-    const char *nhost;
-    int nport;
-    enum alpnid nalpnid;
-    enum alpnid salpnid;
+    enum alpnid srcalpnid;
     bool hit;
+    struct altsvc *as;
+    const int allowed_versions = ( ALPN_h1
+#ifdef USE_NGHTTP2
+      | ALPN_h2
+#endif
+#ifdef ENABLE_QUIC
+      | ALPN_h3
+#endif
+      ) & data->asi->flags;
+
     host = conn->host.rawalloc;
 #ifdef USE_NGHTTP2
     /* with h2 support, check that first */
-    salpnid = ALPN_h2;
+    srcalpnid = ALPN_h2;
     hit = Curl_altsvc_lookup(data->asi,
-                             salpnid, host, conn->remote_port, /* from */
-                             &nalpnid, &nhost, &nport /* to */);
+                             srcalpnid, host, conn->remote_port, /* from */
+                             &as /* to */,
+                             allowed_versions);
     if(!hit)
 #endif
     {
-      salpnid = ALPN_h1;
+      srcalpnid = ALPN_h1;
       hit = Curl_altsvc_lookup(data->asi,
-                               salpnid, host, conn->remote_port, /* from */
-                               &nalpnid, &nhost, &nport /* to */);
+                               srcalpnid, host, conn->remote_port, /* from */
+                               &as /* to */,
+                               allowed_versions);
     }
     if(hit) {
-      char *hostd = strdup((char *)nhost);
+      char *hostd = strdup((char *)as->dst.host);
       if(!hostd)
         return CURLE_OUT_OF_MEMORY;
       conn->conn_to_host.rawalloc = hostd;
       conn->conn_to_host.name = hostd;
       conn->bits.conn_to_host = TRUE;
-      conn->conn_to_port = nport;
+      conn->conn_to_port = as->dst.port;
       conn->bits.conn_to_port = TRUE;
       conn->bits.altused = TRUE;
       infof(data, "Alt-svc connecting from [%s]%s:%d to [%s]%s:%d\n",
-            Curl_alpnid2str(salpnid), host, conn->remote_port,
-            Curl_alpnid2str(nalpnid), hostd, nport);
-      if(salpnid != nalpnid) {
+            Curl_alpnid2str(srcalpnid), host, conn->remote_port,
+            Curl_alpnid2str(as->dst.alpnid), hostd, as->dst.port);
+      if(srcalpnid != as->dst.alpnid) {
         /* protocol version switch */
-        switch(nalpnid) {
+        switch(as->dst.alpnid) {
         case ALPN_h1:
           conn->httpversion = 11;
           break;