[http] Cleanly shut down potentially looped interfaces
[ipxe.git] / src / net / tcp / httpgce.c
1 /*
2 * Copyright (C) 2017 Michael Brown <mbrown@fensystems.co.uk>.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License as
6 * published by the Free Software Foundation; either version 2 of the
7 * License, or any later version.
8 *
9 * This program is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
17 * 02110-1301, USA.
18 *
19 * You can also choose to distribute this program under the terms of
20 * the Unmodified Binary Distribution Licence (as given in the file
21 * COPYING.UBDL), provided that you have satisfied its requirements.
22 */
23
24 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
25
26 /**
27 * @file
28 *
29 * Google Compute Engine (GCE) metadata retrieval
30 *
31 * For some unspecified "security" reason, the Google Compute Engine
32 * metadata server will refuse any requests that do not include the
33 * non-standard HTTP header "Metadata-Flavor: Google".
34 */
35
36 #include <strings.h>
37 #include <stdio.h>
38 #include <ipxe/http.h>
39
40 /** Metadata host name
41 *
42 * This is used to identify metadata requests, in the absence of any
43 * more robust mechanism.
44 */
45 #define GCE_METADATA_HOST_NAME "metadata.google.internal"
46
47 /**
48 * Construct HTTP "Metadata-Flavor" header
49 *
50 * @v http HTTP transaction
51 * @v buf Buffer
52 * @v len Length of buffer
53 * @ret len Length of header value, or negative error
54 */
55 static int http_format_metadata_flavor ( struct http_transaction *http,
56 char *buf, size_t len ) {
57
58 /* Do nothing unless this appears to be a Google Compute
59 * Engine metadata request.
60 */
61 if ( strcasecmp ( http->request.host, GCE_METADATA_HOST_NAME ) != 0 )
62 return 0;
63
64 /* Construct host URI */
65 return snprintf ( buf, len, "Google" );
66 }
67
68 /** HTTP "Metadata-Flavor" header */
69 struct http_request_header http_request_metadata_flavor __http_request_header ={
70 .name = "Metadata-Flavor",
71 .format = http_format_metadata_flavor,
72 };