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authorGravatar Sergey Ponomarev <stokito@gmail.com>2020-08-15 23:52:48 +0200
committerGravatar Denys Vlasenko <vda.linux@googlemail.com>2020-08-15 23:54:48 +0200
commit4864a685967bd098307a0d64293b5de1fc5f8210 (patch)
tree6f2dd2c10582a302c13d1a08dc446a331a87287f
parentb6efac31d864cffdf618744fd8a6fddbdee3eb4b (diff)
downloadbusybox-4864a685967bd098307a0d64293b5de1fc5f8210.tar.gz
busybox-4864a685967bd098307a0d64293b5de1fc5f8210.tar.bz2
httpd: Support caching via ETag header
If server responds with ETag then next time client can resend it via If-None-Match header. Then httpd will check if file wasn't modified and if not return 304 Not Modified status code. The ETag value is constructed from file's last modification date in unix epoch and it's size: "hex(last_mod)-hex(file_size)" e.g. "5e132e20-417" (with quotes). That means that it's not completely reliable as hash functions but fair enough. The same form of ETag is used by Nginx so load balancing of static content is safe. function old new delta handle_incoming_and_exit 2135 2201 +66 http_response 88 96 +8 send_headers 676 683 +7 parse_conf 1362 1365 +3 http_response_type 22 24 +2 send_file_and_exit 847 841 -6 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 5/1 up/down: 86/-6) Total: 80 bytes Signed-off-by: Sergey Ponomarev <stokito@gmail.com> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--networking/httpd.c57
1 files changed, 54 insertions, 3 deletions
diff --git a/networking/httpd.c b/networking/httpd.c
index 94f7297ad..0297cf9ec 100644
--- a/networking/httpd.c
+++ b/networking/httpd.c
@@ -215,6 +215,19 @@
//config: Makes httpd send files using GZIP content encoding if the
//config: client supports it and a pre-compressed <file>.gz exists.
//config:
+//config:config FEATURE_HTTPD_ETAG
+//config: bool "Support caching via ETag header"
+//config: default y
+//config: depends on HTTPD
+//config: help
+//config: If server responds with ETag then next time client (browser)
+//config: resend it via If-None-Match header.
+//config: Then httpd will check if file wasn't modified and if not,
+//config: return 304 Not Modified status code.
+//config: The ETag value is constructed from last modification date
+//config: in unix epoch, and size: "hex(last_mod)-hex(file_size)".
+//config: It's not completely reliable as hash functions but fair enough.
+//config:
//config:config FEATURE_HTTPD_LAST_MODIFIED
//config: bool "Add Last-Modified header to response"
//config: default y
@@ -328,6 +341,7 @@ enum {
HTTP_OK = 200,
HTTP_PARTIAL_CONTENT = 206,
HTTP_MOVED_TEMPORARILY = 302,
+ HTTP_NOT_MODIFIED = 304,
HTTP_BAD_REQUEST = 400, /* malformed syntax */
HTTP_UNAUTHORIZED = 401, /* authentication needed, respond with auth hdr */
HTTP_NOT_FOUND = 404,
@@ -345,7 +359,6 @@ enum {
HTTP_NO_CONTENT = 204,
HTTP_MULTIPLE_CHOICES = 300,
HTTP_MOVED_PERMANENTLY = 301,
- HTTP_NOT_MODIFIED = 304,
HTTP_PAYMENT_REQUIRED = 402,
HTTP_BAD_GATEWAY = 502,
HTTP_SERVICE_UNAVAILABLE = 503, /* overload, maintenance */
@@ -358,6 +371,9 @@ static const uint16_t http_response_type[] ALIGN2 = {
HTTP_PARTIAL_CONTENT,
#endif
HTTP_MOVED_TEMPORARILY,
+#if ENABLE_FEATURE_HTTPD_ETAG
+ HTTP_NOT_MODIFIED,
+#endif
HTTP_REQUEST_TIMEOUT,
HTTP_NOT_IMPLEMENTED,
#if ENABLE_FEATURE_HTTPD_BASIC_AUTH
@@ -374,7 +390,6 @@ static const uint16_t http_response_type[] ALIGN2 = {
HTTP_NO_CONTENT,
HTTP_MULTIPLE_CHOICES,
HTTP_MOVED_PERMANENTLY,
- HTTP_NOT_MODIFIED,
HTTP_BAD_GATEWAY,
HTTP_SERVICE_UNAVAILABLE,
#endif
@@ -389,6 +404,9 @@ static const struct {
{ "Partial Content", NULL },
#endif
{ "Found", NULL },
+#if ENABLE_FEATURE_HTTPD_ETAG
+ { "Not Modified" },
+#endif
{ "Request Timeout", "No request appeared within 60 seconds" },
{ "Not Implemented", "The requested method is not recognized" },
#if ENABLE_FEATURE_HTTPD_BASIC_AUTH
@@ -405,7 +423,6 @@ static const struct {
{ "No Content" },
{ "Multiple Choices" },
{ "Moved Permanently" },
- { "Not Modified" },
{ "Bad Gateway", "" },
{ "Service Unavailable", "" },
#endif
@@ -419,6 +436,9 @@ struct globals {
smallint content_gzip;
#endif
time_t last_mod;
+#if ENABLE_FEATURE_HTTPD_ETAG
+ char *if_none_match;
+#endif
char *rmt_ip_str; /* for $REMOTE_ADDR and $REMOTE_PORT */
const char *bind_addr_or_port;
@@ -453,6 +473,9 @@ struct globals {
#define sizeof_hdr_buf COMMON_BUFSIZE
char *hdr_ptr;
int hdr_cnt;
+#if ENABLE_FEATURE_HTTPD_ETAG
+ char etag[sizeof("'%llx-%llx'") + 2 * sizeof(long long)*3];
+#endif
#if ENABLE_FEATURE_HTTPD_ERROR_PAGES
const char *http_error_page[ARRAY_SIZE(http_response_type)];
#endif
@@ -1208,6 +1231,10 @@ static void send_headers(unsigned responseNum)
#if ENABLE_FEATURE_HTTPD_LAST_MODIFIED
"Last-Modified: %s\r\n"
#endif
+#if ENABLE_FEATURE_HTTPD_ETAG
+ "ETag: %s\r\n"
+#endif
+
/* Because of 4.4 (5), we can forgo sending of "Content-Length"
* since we close connection afterwards, but it helps clients
* to e.g. estimate download times, show progress bars etc.
@@ -1218,6 +1245,9 @@ static void send_headers(unsigned responseNum)
#if ENABLE_FEATURE_HTTPD_LAST_MODIFIED
date_str,
#endif
+#if ENABLE_FEATURE_HTTPD_ETAG
+ G.etag,
+#endif
file_size
);
}
@@ -1730,6 +1760,7 @@ static NOINLINE void send_file_and_exit(const char *url, int what)
}
} else {
fd = open(url, O_RDONLY);
+ /* file_size and last_mod are already populated */
}
if (fd < 0) {
if (DEBUG)
@@ -1741,6 +1772,19 @@ static NOINLINE void send_file_and_exit(const char *url, int what)
send_headers_and_exit(HTTP_NOT_FOUND);
log_and_exit();
}
+#if ENABLE_FEATURE_HTTPD_ETAG
+ /* ETag is "hex(last_mod)-hex(file_size)" e.g. "5e132e20-417" */
+ sprintf(G.etag, "\"%llx-%llx\"", (unsigned long long)last_mod, (unsigned long long)file_size);
+
+ if (G.if_none_match) {
+ if (DEBUG)
+ bb_perror_msg("If-None-Match and file's ETag are: '%s' '%s'\n", G.if_none_match, G.etag);
+ /* Weak ETag comparision.
+ * If-None-Match may have many ETags but they are quoted so we can use simple substring search */
+ if (strstr(G.if_none_match, G.etag))
+ send_headers_and_exit(HTTP_NOT_MODIFIED);
+ }
+#endif
/* If you want to know about EPIPE below
* (happens if you abort downloads from local httpd): */
signal(SIGPIPE, SIG_IGN);
@@ -2480,6 +2524,13 @@ static void handle_incoming_and_exit(const len_and_sockaddr *fromAddr)
continue;
}
#endif
+#if ENABLE_FEATURE_HTTPD_ETAG
+ if (STRNCASECMP(iobuf, "If-None-Match:") == 0) {
+ free(G.if_none_match);
+ G.if_none_match = xstrdup(skip_whitespace(iobuf + sizeof("If-None-Match:") - 1));
+ continue;
+ }
+#endif
#if ENABLE_FEATURE_HTTPD_CGI
if (cgi_type != CGI_NONE) {
bool ct = (STRNCASECMP(iobuf, "Content-Type:") == 0);