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Posted to dev@httpd.apache.org by Justin Erenkrantz <ju...@erenkrantz.com> on 2004/08/05 11:08:29 UTC
[PATCH] mod_disk_cache: Use binary header format
This patch fully fleshes out Brian's earlier patch and tries to optimize
the header on-disk format. The current disk format didn't make any sense.
It also was full of security holes (reading into a 1034-byte char's). Only
the headers are still CRLF-delimited. We could go further and replace
ap_scan_script_header_err(), but I think there are other things to sort out
first. (I believe that the fixes to apr_file_gets() make those calls not
as important to optimize.)
Note this is even extensible - the format field will allow us to hot-deploy
new formats - on a mismatch, it'll overwrite the existing file. -- justin
* modules/experimental/mod_disk_cache.c: Switch to a binary format for
header files.
Index: modules/experimental/mod_disk_cache.c
===================================================================
RCS file: /home/cvspublic/httpd-2.0/modules/experimental/mod_disk_cache.c,v
retrieving revision 1.56
diff -u -r1.56 mod_disk_cache.c
--- modules/experimental/mod_disk_cache.c 5 Aug 2004 08:27:24 -0000 1.56
+++ modules/experimental/mod_disk_cache.c 5 Aug 2004 08:55:01 -0000
@@ -23,6 +23,32 @@
#include <unistd.h> /* needed for unlink/link */
#endif
+/* Our on-disk header format is:
+ *
+ * disk_cache_info_t
+ * entity name (dobj->name)
+ * r->headers_out (delimited by CRLF)
+ * CRLF
+ * r->headers_in (delimited by CRLF)
+ * CRLF
+ */
+#define DISK_FORMAT_VERSION 0
+typedef struct {
+ /* Indicates the format of the header struct stored on-disk. */
+ int format;
+ /* The HTTP status code returned for this response. */
+ int status;
+ /* The size of the entity name that follows. */
+ apr_size_t name_len;
+ /* The number of times we've cached this entity. */
+ apr_size_t entity_version;
+ /* Miscellaneous time values. */
+ apr_time_t date;
+ apr_time_t expire;
+ apr_time_t request_time;
+ apr_time_t response_time;
+} disk_cache_info_t;
+
/*
* disk_cache_object_t
* Pointed to by cache_object_t::vobj
@@ -37,12 +63,13 @@
char *datafile; /* name of file where the data will go */
char *hdrsfile; /* name of file where the hdrs will go */
char *name;
- apr_time_t version; /* update count of the file */
apr_file_t *fd; /* data file */
apr_file_t *hfd; /* headers file */
apr_off_t file_size; /* File size of the cached data file */
+ disk_cache_info_t disk_info; /* Header information. */
} disk_cache_object_t;
+
/*
* mod_disk_cache configuration
*/
@@ -187,104 +214,55 @@
* and written transparent to clients of this module
*/
static int file_cache_recall_mydata(apr_file_t *fd, cache_info *info,
- disk_cache_object_t *dobj)
+ disk_cache_object_t *dobj, request_rec
*r)
{
apr_status_t rv;
- char urlbuff[1034]; /* XXX FIXME... THIS IS A POTENTIAL SECURITY HOLE
*/
- int urllen = sizeof(urlbuff);
- int offset=0;
+ char *urlbuff;
char * temp;
+ disk_cache_info_t disk_info;
+ apr_size_t len;
/* read the data from the cache file */
- /* format
- * date SP expire SP count CRLF
- * dates are stored as a hex representation of apr_time_t (number of
- * microseconds since 00:00:00 January 1, 1970 UTC)
- */
- rv = apr_file_gets(&urlbuff[0], urllen, fd);
+ len = sizeof(disk_cache_info_t);
+ rv = apr_file_read_full(fd, &disk_info, len, &len);
if (rv != APR_SUCCESS) {
return rv;
}
- if ((temp = strchr(&urlbuff[0], '\n')) != NULL) /* trim off new line
character */
- *temp = '\0'; /* overlay it with the null terminator */
-
- if (!apr_date_checkmask(urlbuff, "&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&
&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&")) {
+ if (disk_info.format != DISK_FORMAT_VERSION) {
+ ap_log_error(APLOG_MARK, APLOG_ERR, 0, r->server,
+ "cache_disk: URL %s had a on-disk version mismatch",
+ r->uri);
return APR_EGENERAL;
}
- info->date = ap_cache_hex2usec(urlbuff + offset);
- offset += (sizeof(info->date)*2) + 1;
- info->expire = ap_cache_hex2usec(urlbuff + offset);
- offset += (sizeof(info->expire)*2) + 1;
- dobj->version = ap_cache_hex2usec(urlbuff + offset);
- offset += (sizeof(info->expire)*2) + 1;
- info->request_time = ap_cache_hex2usec(urlbuff + offset);
- offset += (sizeof(info->expire)*2) + 1;
- info->response_time = ap_cache_hex2usec(urlbuff + offset);
+ /* Store it away so we can get it later. */
+ dobj->disk_info = disk_info;
- /* check that we have the same URL */
- rv = apr_file_gets(&urlbuff[0], urllen, fd);
+ info->date = disk_info.date;
+ info->expire = disk_info.expire;
+ info->request_time = disk_info.request_time;
+ info->response_time = disk_info.response_time;
+
+ /* Note that we could optimize this by conditionally doing the palloc
+ * depending upon the size. */
+ urlbuff = apr_palloc(r->pool, disk_info.name_len + 1);
+ len = disk_info.name_len;
+ rv = apr_file_read_full(fd, urlbuff, len, &len);
if (rv != APR_SUCCESS) {
return rv;
}
+ urlbuff[disk_info.name_len] = '\0';
- if ((temp = strchr(&urlbuff[0], '\n')) != NULL) { /* trim off new line
character */
- *temp = '\0'; /* overlay it with the null terminator */
- }
-
- if (strncmp(urlbuff, "X-NAME: ", 7) != 0) {
- return APR_EGENERAL;
- }
- if (strcmp(urlbuff + 8, dobj->name) != 0) {
+ /* check that we have the same URL */
+ /* Would strncmp be correct? */
+ if (strcmp(urlbuff, dobj->name) != 0) {
return APR_EGENERAL;
}
return APR_SUCCESS;
}
-static int file_cache_store_mydata(apr_file_t *fd , cache_handle_t *h,
request_rec *r)
-{
- apr_status_t rc;
- char *buf;
- apr_size_t amt;
-
- char dateHexS[sizeof(apr_time_t) * 2 + 1];
- char expireHexS[sizeof(apr_time_t) * 2 + 1];
- char verHexS[sizeof(apr_time_t) * 2 + 1];
- char requestHexS[sizeof(apr_time_t) * 2 + 1];
- char responseHexS[sizeof(apr_time_t) * 2 + 1];
- cache_info *info = &(h->cache_obj->info);
- disk_cache_object_t *dobj = (disk_cache_object_t *) h->cache_obj->vobj;
-
- if (!r->headers_out) {
- /* XXX log message */
- return 0;
- }
-
- ap_cache_usec2hex(info->date, dateHexS);
- ap_cache_usec2hex(info->expire, expireHexS);
- ap_cache_usec2hex(dobj->version++, verHexS);
- ap_cache_usec2hex(info->request_time, requestHexS);
- ap_cache_usec2hex(info->response_time, responseHexS);
- buf = apr_pstrcat(r->pool, dateHexS, " ", expireHexS, " ", verHexS, "
", requestHexS, " ", responseHexS, "\n", NULL);
- amt = strlen(buf);
- rc = apr_file_write(fd, buf, &amt);
- if (rc != APR_SUCCESS) {
- /* XXX log message */
- return 0;
- }
-
- buf = apr_pstrcat(r->pool, "X-NAME: ", dobj->name, "\n", NULL);
- amt = strlen(buf);
- rc = apr_file_write(fd, buf, &amt);
- if (rc != APR_SUCCESS) {
- /* XXX log message */
- return 0;
- }
- return 1;
-}
-
/*
* Hook and mod_cache callback functions
*/
@@ -430,7 +408,7 @@
}
/* Read the bytes to setup the cache_info fields */
- rc = file_cache_recall_mydata(hfd, info, dobj);
+ rc = file_cache_recall_mydata(hfd, info, dobj, r);
if (rc != APR_SUCCESS) {
/* XXX log message */
return DECLINED;
@@ -465,8 +443,6 @@
static apr_status_t recall_headers(cache_handle_t *h, request_rec *r)
{
apr_status_t rv;
- char urlbuff[1034];
- int urllen = sizeof(urlbuff);
disk_cache_object_t *dobj = (disk_cache_object_t *) h->cache_obj->vobj;
apr_table_t * tmp;
@@ -483,36 +459,22 @@
/*
* Call routine to read the header lines/status line
*/
+ r->status = dobj->disk_info.status;
ap_scan_script_header_err(r, dobj->hfd, NULL);
apr_table_setn(r->headers_out, "Content-Type",
ap_make_content_type(r, r->content_type));
- rv = apr_file_gets(&urlbuff[0], urllen, dobj->hfd); /* Read
status */
- if (rv != APR_SUCCESS) {
- /* XXX log message */
- return rv;
- }
-
- r->status = atoi(urlbuff); /* Save status
line into request rec */
-
- /* Read and ignore the status line (This request might result in a
- * 304, so we don't necessarily want to retransmit a 200 from the
cache.)
- */
- rv = apr_file_gets(&urlbuff[0], urllen, dobj->hfd);
- if (rv != APR_SUCCESS) {
- /* XXX log message */
- return rv;
- }
-
h->req_hdrs = apr_table_make(r->pool, 20);
/*
* Call routine to read the header lines/status line
+ *
+ * Note that ap_scan_script_header_err sets to r->err_headers_out,
+ * so we must set the real one aside.
*/
tmp = r->err_headers_out;
r->err_headers_out = h->req_hdrs;
- rv = apr_file_gets(&urlbuff[0], urllen, dobj->hfd); /* Read
status */
ap_scan_script_header_err(r, dobj->hfd, NULL);
r->err_headers_out = tmp;
@@ -537,6 +499,40 @@
return APR_SUCCESS;
}
+static apr_status_t store_table(apr_file_t *fd, apr_table_t *table)
+{
+ int i;
+ apr_status_t rv;
+ struct iovec iov[4];
+ apr_size_t amt;
+ apr_table_entry_t *elts;
+
+ elts = (apr_table_entry_t *) apr_table_elts(table)->elts;
+ for (i = 0; i < apr_table_elts(table)->nelts; ++i) {
+ if (elts[i].key != NULL) {
+ iov[0].iov_base = elts[i].key;
+ iov[0].iov_len = strlen(elts[i].key);
+ iov[1].iov_base = ": ";
+ iov[1].iov_len = sizeof(": ") - 1;
+ iov[2].iov_base = elts[i].val;
+ iov[2].iov_len = strlen(elts[i].val);
+ iov[3].iov_base = CRLF;
+ iov[3].iov_len = sizeof(CRLF) - 1;
+
+ rv = apr_file_writev(fd, (const struct iovec *) &iov, 4,
+ &amt);
+ if (rv != APR_SUCCESS) {
+ return rv;
+ }
+ }
+ }
+ iov[0].iov_base = CRLF;
+ iov[0].iov_len = sizeof(CRLF) - 1;
+ rv = apr_file_writev(fd, (const struct iovec *) &iov, 1,
+ &amt);
+ return rv;
+}
+
static apr_status_t store_headers(cache_handle_t *h, request_rec *r,
cache_info *info)
{
disk_cache_conf *conf = ap_get_module_config(r->server->module_config,
@@ -549,6 +545,9 @@
apr_file_t *hfd = dobj->hfd;
if (!hfd) {
+ disk_cache_info_t disk_info;
+ struct iovec iov[2];
+
if (!dobj->hdrsfile) {
dobj->hdrsfile = header_file(r->pool,
conf->dirlevels,
@@ -578,22 +577,40 @@
hfd = dobj->hfd;
dobj->name = h->cache_obj->key;
- file_cache_store_mydata(dobj->hfd, h, r);
+ disk_info.format = DISK_FORMAT_VERSION;
+ disk_info.date = info->date;
+ disk_info.expire = info->expire;
+ disk_info.entity_version = dobj->disk_info.entity_version++;
+ disk_info.request_time = info->request_time;
+ disk_info.response_time = info->response_time;
+
+ disk_info.name_len = strlen(dobj->name);
+ disk_info.status = r->status;
+
+ /* This case only occurs when the content is generated locally */
+ if (!r->status_line) {
+ r->status_line = ap_get_status_line(r->status);
+ }
+
+ iov[0].iov_base = &disk_info;
+ iov[0].iov_len = sizeof(disk_cache_info_t);
+ iov[1].iov_base = dobj->name;
+ iov[1].iov_len = disk_info.name_len;
+
+ rv = apr_file_writev(hfd, (const struct iovec *) &iov, 2, &amt);
+ if (rv != APR_SUCCESS) {
+ return rv;
+ }
if (r->headers_out) {
- int i;
- apr_table_t* headers_out =
ap_cache_cacheable_hdrs_out(r->pool, r->headers_out);
- apr_table_entry_t *elts = (apr_table_entry_t *)
apr_table_elts(headers_out)->elts;
- for (i = 0; i < apr_table_elts(headers_out)->nelts; ++i) {
- if (elts[i].key != NULL) {
- buf = apr_pstrcat(r->pool, elts[i].key, ": ",
elts[i].val, CRLF, NULL);
- amt = strlen(buf);
- apr_file_write(hfd, buf, &amt);
- }
+ apr_table_t *headers_out;
+
+ headers_out = ap_cache_cacheable_hdrs_out(r->pool,
r->headers_out);
+
+ rv = store_table(hfd, headers_out);
+ if (rv != APR_SUCCESS) {
+ return rv;
}
- buf = apr_pstrcat(r->pool, CRLF, NULL);
- amt = strlen(buf);
- apr_file_write(hfd, buf, &amt);
/* This case only occurs when the content is generated locally
*/
if (!apr_table_get(r->headers_out, "Content-Type") &&
r->content_type) {
@@ -601,38 +618,15 @@
ap_make_content_type(r, r->content_type));
}
}
- sprintf(statusbuf,"%d", r->status);
- buf = apr_pstrcat(r->pool, statusbuf, CRLF, NULL);
- amt = strlen(buf);
- apr_file_write(hfd, buf, &amt);
- /* This case only occurs when the content is generated locally */
- if (!r->status_line) {
- r->status_line = ap_get_status_line(r->status);
- }
- buf = apr_pstrcat(r->pool, r->status_line, "\n", NULL);
- amt = strlen(buf);
- apr_file_write(hfd, buf, &amt);
- buf = apr_pstrcat(r->pool, CRLF, NULL);
- amt = strlen(buf);
- apr_file_write(hfd, buf, &amt);
-
- /* Parse the vary header and dump those fields from the headers_in. */
- /* Make call to the same thing cache_select_url calls to crack Vary. */
- /* @@@ Some day, not today. */
+ /* Parse the vary header and dump those fields from the
headers_in. */
+ /* Make call to the same thing cache_select_url calls to crack
Vary. */
+ /* @@@ Some day, not today. */
if (r->headers_in) {
- int i;
- apr_table_entry_t *elts = (apr_table_entry_t *)
apr_table_elts(r->headers_in)->elts;
- for (i = 0; i < apr_table_elts(r->headers_in)->nelts; ++i) {
- if (elts[i].key != NULL) {
- buf = apr_pstrcat(r->pool, elts[i].key, ": ",
elts[i].val, CRLF, NULL);
- amt = strlen(buf);
- apr_file_write(hfd, buf, &amt);
- }
+ rv = store_table(hfd, r->headers_in);
+ if (rv != APR_SUCCESS) {
+ return rv;
}
- buf = apr_pstrcat(r->pool, CRLF, NULL);
- amt = strlen(buf);
- apr_file_write(hfd, buf, &amt);
}
apr_file_close(hfd); /* flush and close */
}