If a request is finalized in the first call to the
ngx_http_upstream_process_upgraded() function, e.g., because upstream
server closed the connection for some reason, in the second call
the u->peer.connection pointer will be null, resulting in segmentation
fault.
Fix is to avoid second direct call, and post event instead. This ensures
that ngx_http_upstream_process_upgraded() won't be called again if
a request is finalized.
If "proxy_pass" is specified with variables, the resulting
hostname is looked up in the list of upstreams defined in
configuration. The search was case-sensitive, as opposed
to the case of "proxy_pass" specified without variables.
Read event on a client connection might have been disabled during
previous processing, and we at least need to handle events. Calling
ngx_http_upstream_process_upgraded() is a simpliest way to do it.
Notably this change is needed for select, poll and /dev/poll event
methods.
Previous version of this patch was posted here:
http://mailman.nginx.org/pipermail/nginx/2014-January/041839.html
Not really a strict check (as X-Accel-Expires might be ignored or
contain invalid value), but quite simple to implement and better
than what we have now.
The following new directives are introduced: proxy_cache_revalidate,
fastcgi_cache_revalidate, scgi_cache_revalidate, uwsgi_cache_revalidate.
Default is off. When set to on, they enable cache revalidation using
conditional requests with If-Modified-Since for expired cache items.
As of now, no attempts are made to merge headers given in a 304 response
during cache revalidation with headers previously stored in a cache item.
Headers in a 304 response are only used to calculate new validity time
of a cache item.
With previous code only part of u->buffer might be emptied in case
of special responses, resulting in partial responses seen by SSI set
in case of simple protocols, or spurious errors like "upstream sent
invalid chunked response" in case of complex ones.
Without u->header_sent set a special response might be generated following
an upgraded connection. The problem appeared in 1ccdda1f37f3 (1.5.3).
Catched by "header already sent" alerts in 1.5.4 after upstream timeouts.
Missing call to ngx_http_run_posted_request() resulted in a main request hang
if subrequest's ssl handshake with an upstream server failed for some reason.
Reported by Aviram Cohen.
Previously, after sending a header we always sent a last buffer and
finalized a request with code 0, even in case of errors. In some cases
this resulted in a loss of ability to detect the response wasn't complete
(e.g. if Content-Length was removed from a response by gzip filter).
This change tries to propogate to a client information that a response
isn't complete in such cases. In particular, with this change we no longer
pretend a returned response is complete if we wasn't able to create
a temporary file.
If an error code suggests the error wasn't fatal, we flush buffered data
and disable keepalive, then finalize request normally. This allows to to
propogate information about a problem to a client, while still sending all
the data we've got from an upstream.
No semantic changes expected, though some checks are done differently.
In particular, the r->cached flag is no longer explicitly checked. Instead,
we relay on u->header_sent not being set if a response is sent from
a cache.
The NGX_HTTP_CLIENT_CLOSED_REQUEST code is allowed to happen after we
started sending a response (much like NGX_HTTP_REQUEST_TIME_OUT), so there
is no need to reset response code to 0 in this case.
Checks were added to both buffered and unbuffered code paths to detect
and complain if a response is incomplete. Appropriate error codes are
now passed to ngx_http_upstream_finalize_request().
With this change in unbuffered mode we now use u->length set to -1 as an
indicator that EOF is allowed per protocol and used to indicate response
end (much like its with p->length in buffered mode). Proxy module was
changed to set u->length to 1 (instead of previously used -1) in case of
chunked transfer encoding used to comply with the above.
That is, by default we assume that response end is signalled by
a connection close. This seems to be better default, and in line
with u->pipe->length behaviour.
Memcached module was modified accordingly.
In case of upstream eof, only responses with u->pipe->length == -1
are now cached/stored. This ensures that unfinished chunked responses
are not cached.
Note well - previously used checks for u->headers_in.content_length_n are
preserved. This provides an additional level of protection if protol data
disagree with Content-Length header provided (e.g., a FastCGI response
is sent with wrong Content-Length, or an incomple SCGI or uwsgi response),
as well as protects from storing of responses to HEAD requests. This should
be reconsidered if we'll consider caching of responses to HEAD requests.
There is no real difference from previously used 0 as NGX_HTTP_* will
become 0 in ngx_http_upstream_finalize_request(), but the change
preserves information about a timeout a bit longer. Previous use of
ETIMEDOUT in one place was just wrong.
Note well that with cacheable responses there will be a difference
(code in ngx_http_upstream_finalize_request() will store the error
in cache), though this change doesn't touch cacheable case.
Previously, ngx_http_upstream_finalize_request(0) was used in most
cases after errors. While with current code there is no difference,
use of NGX_ERROR allows to pass a bit more information into
ngx_http_upstream_finalize_request().
In all cases ngx_http_upstream_finalize_request() with NGX_ERROR now used.
Previously used NGX_HTTP_INTERNAL_SERVER_ERROR in the subrequest in memory
case don't cause any harm, but inconsistent with other uses.
The parameter is mostly identical to http_404, and is expected to
be used in similar situations. The 403 code might be returned by
a backend instead of 404 on initial sync of new directories with rsync.
See here for feature request and additional details:
http://mailman.nginx.org/pipermail/nginx-ru/2013-April/050920.html
If proxy_pass to a host with dynamic resolution was used to handle
a subrequest, and host resolution failed, the main request wasn't run
till something else happened on the connection. E.g. request to "/zzz"
with the following configuration hanged:
addition_types *;
resolver 8.8.8.8;
location /test {
set $ihost xxx;
proxy_pass http://$ihost;
}
location /zzz {
add_after_body /test;
return 200 "test";
}
Report and original version of the patch by Lanshun Zhou,
http://mailman.nginx.org/pipermail/nginx-devel/2013-March/003476.html.
The c->single_connection was intended to be used as lock mechanism
to serialize modifications of request object from several threads
working with client and upstream connections. The flag is redundant
since threads in nginx have never been used that way.
This allows to proxy WebSockets by using configuration like this:
location /chat/ {
proxy_pass http://backend;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
}
Connection upgrade is allowed as long as it was requested by a client
via the Upgrade request header.
The "proxy_bind", "fastcgi_bind", "uwsgi_bind", "scgi_bind" and
"memcached_bind" directives are now inherited; inherited value
can be reset by the "off" parameter. Duplicate directives are
now detected. Parameter value can now contain variables.
Upstreams created by "proxy_pass" with IP address and no port were
broken in 1.3.10, by not initializing port in u->sockaddr.
API change: ngx_parse_url() was modified to always initialize port
(in u->sockaddr and in u->port), even for the u->no_resolve case;
ngx_http_upstream() and ngx_http_upstream_add() were adopted.
Configuration like
location / {
set $true 1;
if ($true) {
proxy_pass http://backend;
}
if ($true) {
# nothing
}
}
resulted in segmentation fault due to NULL pointer dereference as the
upstream configuration wasn't initialized in an implicit location created
by the last if(), but the r->content_handler was set due to first if().
Instead of committing a suicide by dereferencing a NULL pointer, return
500 (Internal Server Error) in such cases, i.e. if uscf is NULL. Better
fix would be to avoid such cases by fixing the "if" directive handling,
but it's out of scope of this patch.
Prodded by Piotr Sikora.
