mod_proxy: Handle backend address renewal with address_ttl= parameter.

Define a new proxy_address struct holding the current/latest sockaddr in use
by each proxy worker and conn. Since backend addresses can be updated when
their TTL expires and while connections are being processed, each address is
refcounted and freed only when the last worker (or conn) using it grabs the
new one.

The lifetime of the addresses is handled at a single place by the new
ap_proxy_determine_address() function. It guarantees to bind the current/latest
backend address to the passed in conn (or do nothing if it's up to date already).
The function is called indirectly by ap_proxy_determine_connection() for the
proxy modules that use it, or directly by mod_proxy_ftp and mod_proxy_hcheck.
It also is called eventually by ap_proxy_connect_backend() when connect()ing all
the current addresses fails, to check (PROXY_DETERMINE_ADDRESS_CHECK) if some
new addrs are available.

This commit is also a rework of the lifetime of conn->addr, conn->hostname
and conn->forward, using the conn->uds_pool and conn->fwd_pool for the cases
where the backend is connected through a UDS socket and a remote CONNECT proxy
respectively.

* include/ap_mmn.h:
  Minor bump for new function/fields.

* modules/proxy/mod_proxy.h (struct proxy_address,
                             ap_proxy_determine_addresss()):
  Declare ap_proxy_determine_addresss() and opaque struct proxy_address,
  new fields to structs proxy_conn_rec/proxy_worker_shared/proxy_worker.

* modules/proxy/mod_proxy.c (set_worker_param):
  Parse/set the new worker->address_ttl parameter.

* modules/proxy/proxy_util.c (proxy_util_register_hooks(),
                              ap_proxy_initialize_worker(),
                              ap_proxy_connection_reusable(),
                              ap_proxyerror(), proxyerror_core(),
                              init_conn_pool(), make_conn_subpool(),
                              connection_make(), connection_cleanup(),
                              connection_constructor()):
 Initialize *proxy_start_time in proxy_util_register_hooks() as the epoch
 from which expiration times are relative (i.e. seconds stored in an uint32_t
 for atomic changes).
 Make sure worker->s->is_address_reusable and worker->s->disablereuse are
 consistant in ap_proxy_initialize_worker(), thus no need to check for both
 in ap_proxy_connection_reusable().
 New proxyerror_core() helper taking an apr_status_t to log, wrap in
 ap_proxyerror().
 New make_conn_subpool() to create worker->cp->{pool,dns} with their own
 allocator.
 New connection_make() helper to factorize code in connection_cleanup() and
 connection_constructor().

* modules/proxy/proxy_util.c (proxy_address_inc(), proxy_address_dec(),
                              proxy_address_cleanup(), proxy_address_set_expired(),
                              worker_address_get(), worker_address_set(),
                              worker_address_resolve(), proxy_addrs_equal(),
                              ap_proxy_determine_address(),
                              ap_proxy_determine_connection(),
                              ap_proxy_connect_backend()):
 Implement ap_proxy_determine_address() using the above helpers for atomic changes,
 and call it from ap_proxy_determine_connection() and ap_proxy_connect_backend().

* modules/proxy/mod_proxy_ftp.c (proxy_ftp_handler):
  Use ap_proxy_determine_address() and use the returned backend->addr.

* modules/proxy/mod_proxy_hcheck.c (hc_determine_connection, hc_get_backend,
                                    hc_init_worker, hc_watchdog_callback):
  Use ap_proxy_determine_address() in hc_determine_connection() and call the
  latter from hc_get_backend(), replace hc_init_worker() by hc_init_baton()
  which now calls hc_get_hcworker() and hc_get_backend() to resolve the first
  address at init time.

* modules/proxy/mod_proxy_http.c (proxy_http_handler):
  Use backend->addr and ->hostname instead of worker->cp->addr and
  worker->s->hostname_ex respectively.

* modules/proxy/mod_proxy_ajp.c (ap_proxy_ajp_request):
  Use backend->addr and ->hostname instead of worker->cp->addr and
  worker->s->hostname_ex respectively.


Closes #367



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1912459 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 2 insertions, 1 deletions

diff --git a/include/ap_mmn.h b/include/ap_mmn.h
index 59af7ae082..9028490429 100644
--- a/include/ap_mmn.h
+++ b/include/ap_mmn.h
@@ -719,6 +719,7 @@
  *                         than username / password. Add autht_provider structure.
  * 20211221.14 (2.5.1-dev) Add request_rec->final_resp_passed bit
  * 20211221.15 (2.5.1-dev) Add ap_get_pollfd_from_conn()
+ * 20211221.16 (2.5.1-dev) Add ap_proxy_determine_address()
  */
 
 #define MODULE_MAGIC_COOKIE 0x41503235UL /* "AP25" */
@@ -726,7 +727,7 @@
 #ifndef MODULE_MAGIC_NUMBER_MAJOR
 #define MODULE_MAGIC_NUMBER_MAJOR 20211221
 #endif
-#define MODULE_MAGIC_NUMBER_MINOR 15             /* 0...n */
+#define MODULE_MAGIC_NUMBER_MINOR 16             /* 0...n */
 
 /**
  * Determine if the server's current MODULE_MAGIC_NUMBER is at least a