avformat/http: Don't bail on parsing headers on "bad" HTTP codes

Many "bad" HTTP codes like 429 and 503 may include important info in
their headers.

Also, in general, there is no purpose in bailing here.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

libavformat/http.c

@@ -1087,7 +1087,7 @@ static void parse_cache_control(HTTPContext *s, const char *p)
     }
 }
 
-static int process_line(URLContext *h, char *line, int line_count)
+static int process_line(URLContext *h, char *line, int line_count, int *parsed_http_code)
 {
     HTTPContext *s = h->priv_data;
     const char *auto_method =  h->flags & AVIO_FLAG_READ ? "POST" : "GET";
@@ -1167,6 +1167,8 @@ static int process_line(URLContext *h, char *line, int line_count)
 
             av_log(h, AV_LOG_TRACE, "http_code=%d\n", s->http_code);
 
+            *parsed_http_code = 1;
+
             if ((ret = check_http_code(h, s->http_code, end)) < 0)
                 return ret;
         }
@@ -1339,7 +1341,7 @@ static int http_read_header(URLContext *h)
 {
     HTTPContext *s = h->priv_data;
     char line[MAX_URL_SIZE];
-    int err = 0;
+    int err = 0, http_err = 0;
 
     av_freep(&s->new_location);
     s->expires = 0;
@@ -1347,18 +1349,31 @@ static int http_read_header(URLContext *h)
     s->filesize_from_content_range = UINT64_MAX;
 
     for (;;) {
+        int parsed_http_code = 0;
+
         if ((err = http_get_line(s, line, sizeof(line))) < 0)
             return err;
 
         av_log(h, AV_LOG_TRACE, "header='%s'\n", line);
 
-        err = process_line(h, line, s->line_count);
-        if (err < 0)
-            return err;
+        err = process_line(h, line, s->line_count, &parsed_http_code);
+        if (err < 0) {
+            if (parsed_http_code) {
+                http_err = err;
+            } else {
+                /* Prefer to return HTTP code error if we've already seen one. */
+                if (http_err)
+                    return http_err;
+                else
+                    return err;
+            }
+        }
         if (err == 0)
             break;
         s->line_count++;
     }
+    if (http_err)
+        return http_err;
 
     // filesize from Content-Range can always be used, even if using chunked Transfer-Encoding
     if (s->filesize_from_content_range != UINT64_MAX)