retry without partial data after a 416 response

If we get a 416 from the server it means the Range we asked for is above
the real filesize of the file on the server. Mostly this happens if the
server isn't supporting If-Range, but regardless of how we end up with
the partial data, the data is invalid so we discard it and retry with a
fresh plate and hope for the best.

Old behavior was to consider 416 an error and retry with a different
compression until we ran out of compression and requested the
uncompressed file (which doesn't exist on most mirrors) with an accept
line which server answered with "406 Not Acceptable".

Closes: 710924

1 files changed, 17 insertions, 2 deletions

diff --git a/methods/http.cc b/methods/http.cc
index 278ddb290..2a8b7f0fc 100644
--- a/methods/http.cc
+++ b/methods/http.cc
@@ -604,6 +604,8 @@ bool ServerState::HeaderLine(string Line)
       Size = strtoull(Val.c_str(), NULL, 10);
       if (Size >= std::numeric_limits<unsigned long long>::max())
 	 return _error->Errno("HeaderLine", _("The HTTP server sent an invalid Content-Length header"));
+      else if (Size == 0)
+	 HaveContent = false;
       return true;
    }
 
@@ -616,8 +618,14 @@ bool ServerState::HeaderLine(string Line)
    if (stringcasecmp(Tag,"Content-Range:") == 0)
    {
       HaveContent = true;
-      
-      if (sscanf(Val.c_str(),"bytes %llu-%*u/%llu",&StartPos,&Size) != 2)
+
+      // §14.16 says 'byte-range-resp-spec' should be a '*' in case of 416
+      if (Result == 416 && sscanf(Val.c_str(), "bytes */%llu",&Size) == 1)
+      {
+	 StartPos = 1; // ignore Content-Length, it would override Size
+	 HaveContent = false;
+      }
+      else if (sscanf(Val.c_str(),"bytes %llu-%*u/%llu",&StartPos,&Size) != 2)
 	 return _error->Error(_("The HTTP server sent an invalid Content-Range header"));
       if ((unsigned long long)StartPos > Size)
 	 return _error->Error(_("This HTTP server has broken range support"));
@@ -995,6 +1003,13 @@ HttpMethod::DealWithHeaders(FetchResult &Res,ServerState *Srv)
       }
       /* else pass through for error message */
    }
+   // retry after an invalid range response without partial data
+   else if (Srv->Result == 416 && FileExists(Queue->DestFile) == true &&
+	 unlink(Queue->DestFile.c_str()) == 0)
+   {
+      NextURI = Queue->Uri;
+      return TRY_AGAIN_OR_REDIRECT;
+   }
  
    /* We have a reply we dont handle. This should indicate a perm server
       failure */