debuginfod: PR27277 - Describe retrieved files when verbosensanci/verbose-headers

There appear to exist use cases that intend to simply check for the
existence of content in a debuginfod server, without actually
downloading it.  In HTTP land, the HEAD operation is the natural
expression of this.
Instead of implementing a HEAD/describe option, allow users, with enough
verbosity, to print the HTTP response headers upon retrieving a file.
E.g output:

HTTP/1.1 200 OK
Connection: Keep-Alive
Content-Length: 2428240
Cache-Control: public
Last-Modified: Sat, 15 May 2021 20:49:51 GMT
X-FILE: "file name"
X-FILE-SIZE: "byte length of file"
Content-Type: application/octet-stream
Date: Tue, 03 Aug 2021 18:50:36 GMT

https://sourceware.org/bugzilla/show_bug.cgi?id=27277

Signed-off-by: Noah Sanci <nsanci@redhat.com>

1 files changed, 54 insertions, 4 deletions

diff --git a/debuginfod/debuginfod-client.c b/debuginfod/debuginfod-client.c
index 7d4b220f..eb52dddf 100644
--- a/debuginfod/debuginfod-client.c
+++ b/debuginfod/debuginfod-client.c
@@ -127,6 +127,7 @@ struct debuginfod_client
      timeout or other info gotten from environment variables, the
      handle data, etc. So those don't have to be reparsed and
      recreated on each request.  */
+  char * winning_headers;
 };
 
 /* The cache_clean_interval_s file within the debuginfod cache specifies
@@ -183,6 +184,8 @@ struct handle_data
      to the cache. Used to ensure that a file is not downloaded from
      multiple servers unnecessarily.  */
   CURL **target_handle;
+  /* Response http headers for this client handle, sent from the server */
+  char *response_data;
 };
 
 static size_t
@@ -499,6 +502,33 @@ default_progressfn (debuginfod_client *c, long a, long b)
 }
 
 
+static size_t
+header_callback (char * buffer, size_t size, size_t numitems, void * userdata)
+{
+  if (size != 1)
+    return 0;
+  /* Temporary buffer for realloc */
+  char *temp = NULL;
+  size_t userlen = 0;
+  if (*(char**)userdata == NULL)
+    {
+      temp = malloc(numitems+1);
+      if (temp == NULL)
+        return 0;
+      memset(temp, '\0', numitems+1);
+    }
+  else
+    {
+      userlen = strlen(*(char**)userdata);
+      temp = realloc(*(char**)userdata, userlen + numitems + 1);
+      if (temp == NULL)
+       return 0;
+    }
+  strncat(temp, buffer, numitems);
+  *(char**)userdata = temp;
+  return numitems;
+}
+
 /* Query each of the server URLs found in $DEBUGINFOD_URLS for the file
    with the specified build-id, type (debuginfo, executable or source)
    and filename. filename may be NULL. If found, return a file
@@ -936,10 +966,13 @@ debuginfod_query_server (debuginfod_client *c,
 	  curl_easy_setopt (data[i].handle, CURLOPT_LOW_SPEED_LIMIT,
 			    100 * 1024L);
 	}
+      data[i].response_data = NULL;
       curl_easy_setopt(data[i].handle, CURLOPT_FILETIME, (long) 1);
       curl_easy_setopt(data[i].handle, CURLOPT_FOLLOWLOCATION, (long) 1);
       curl_easy_setopt(data[i].handle, CURLOPT_FAILONERROR, (long) 1);
       curl_easy_setopt(data[i].handle, CURLOPT_NOSIGNAL, (long) 1);
+      curl_easy_setopt(data[i].handle, CURLOPT_HEADERFUNCTION, header_callback);
+      curl_easy_setopt(data[i].handle, CURLOPT_HEADERDATA, (void *) &(data[i].response_data));
 #if LIBCURL_VERSION_NUM >= 0x072a00 /* 7.42.0 */
       curl_easy_setopt(data[i].handle, CURLOPT_PATH_AS_IS, (long) 1);
 #else
@@ -961,6 +994,7 @@ debuginfod_query_server (debuginfod_client *c,
   int committed_to = -1;
   bool verbose_reported = false;
   struct timespec start_time, cur_time;
+  c->winning_headers = NULL;
   if ( maxtime > 0 && clock_gettime(CLOCK_MONOTONIC_RAW, &start_time) == -1)
     {
       rc = errno;
@@ -995,8 +1029,18 @@ debuginfod_query_server (debuginfod_client *c,
 	    if (data[i].handle != target_handle)
 	      curl_multi_remove_handle(curlm, data[i].handle);
 	    else
-	      committed_to = i;
-	}
+              {
+	        committed_to = i;
+                if (c->winning_headers == NULL)
+                  {
+                    c->winning_headers = data[committed_to].response_data;
+                    if (vfd >= 0 && c->winning_headers != NULL)
+                      dprintf(vfd, "\n%s", c->winning_headers);
+                    data[committed_to].response_data = NULL;
+                  }
+
+              }
+        }
 
       if (vfd >= 0 && !verbose_reported && committed_to >= 0)
 	{
@@ -1161,10 +1205,10 @@ debuginfod_query_server (debuginfod_client *c,
                 {
                   char *effective_url = NULL;
                   long resp_code = 500;
-                  CURLcode ok1 = curl_easy_getinfo (target_handle,
+                  CURLcode ok1 = curl_easy_getinfo (msg->easy_handle,
 						    CURLINFO_EFFECTIVE_URL,
 						    &effective_url);
-                  CURLcode ok2 = curl_easy_getinfo (target_handle,
+                  CURLcode ok2 = curl_easy_getinfo (msg->easy_handle,
 						    CURLINFO_RESPONSE_CODE,
 						    &resp_code);
                   if(ok1 == CURLE_OK && ok2 == CURLE_OK && effective_url)
@@ -1238,7 +1282,10 @@ debuginfod_query_server (debuginfod_client *c,
             {
               curl_multi_remove_handle(curlm, data[i].handle); /* ok to repeat */
               curl_easy_cleanup (data[i].handle);
+              free(data[i].response_data);
             }
+            free(c->winning_headers);
+            c->winning_headers = NULL;
 	    goto query_in_parallel;
 	}
       else
@@ -1281,6 +1328,7 @@ debuginfod_query_server (debuginfod_client *c,
     {
       curl_multi_remove_handle(curlm, data[i].handle); /* ok to repeat */
       curl_easy_cleanup (data[i].handle);
+      free (data[i].response_data);
     }
 
   for (int i = 0; i < num_urls; ++i)
@@ -1304,6 +1352,7 @@ debuginfod_query_server (debuginfod_client *c,
     {
       curl_multi_remove_handle(curlm, data[i].handle); /* ok to repeat */
       curl_easy_cleanup (data[i].handle);
+      free (data[i].response_data);
     }
 
   unlink (target_cache_tmppath);
@@ -1415,6 +1464,7 @@ debuginfod_end (debuginfod_client *client)
 
   curl_multi_cleanup (client->server_mhandle);
   curl_slist_free_all (client->headers);
+  free (client->winning_headers);
   free (client->url);
   free (client);
 }