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lib: introduce struct easy_poll_set for poll information

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Connection filter had a `get_select_socks()` method, inspired by the
various `getsocks` functions involved during the lifetime of a
transfer. These, depending on transfer state (CONNECT/DO/DONE/ etc.),
return sockets to monitor and flag if this shall be done for POLLIN
and/or POLLOUT.

Due to this design, sockets and flags could only be added, not
removed. This led to problems in filters like HTTP/2 where flow control
prohibits the sending of data until the peer increases the flow
window. The general transfer loop wants to write, adds POLLOUT, the
socket is writeable but no data can be written.

This leads to cpu busy loops. To prevent that, HTTP/2 did set the
`SEND_HOLD` flag of such a blocked transfer, so the transfer loop cedes
further attempts. This works if only one such filter is involved. If a
HTTP/2 transfer goes through a HTTP/2 proxy, two filters are
setting/clearing this flag and may step on each other's toes.

Connection filters `get_select_socks()` is replaced by
`adjust_pollset()`. They get passed a `struct easy_pollset` that keeps
up to `MAX_SOCKSPEREASYHANDLE` sockets and their `POLLIN|POLLOUT`
flags. This struct is initialized in `multi_getsock()` by calling the
various `getsocks()` implementations based on transfer state, as before.

After protocol handlers/transfer loop have set the sockets and flags
they want, the `easy_pollset` is *always* passed to the filters. Filters
"higher" in the chain are called first, starting at the first
not-yet-connection one. Each filter may add sockets and/or change
flags. When all flags are removed, the socket itself is removed from the
pollset.

Example:

 * transfer wants to send, adds POLLOUT
 * http/2 filter has a flow control block, removes POLLOUT and adds
   POLLIN (it is waiting on a WINDOW_UPDATE from the server)
 * TLS filter is connected and changes nothing
 * h2-proxy filter also has a flow control block on its tunnel stream,
   removes POLLOUT and adds POLLIN also.
 * socket filter is connected and changes nothing
 * The resulting pollset is then mixed together with all other transfers
   and their pollsets, just as before.

Use of `SEND_HOLD` is no longer necessary in the filters.

All filters are adapted for the changed method. The handling in
`multi.c` has been adjusted, but its state handling the the protocol
handlers' `getsocks` method are untouched.

The most affected filters are http/2, ngtcp2, quiche and h2-proxy. TLS
filters needed to be adjusted for the connecting handshake read/write
handling.

No noticeable difference in performance was detected in local scorecard
runs.

Closes #11833
This commit is contained in:
Stefan Eissing 2023-09-04 12:06:07 +02:00 • committed by Daniel Stenberg
parent 29e198bc71
commit 47f5b1a37f
No known key found for this signature in database
GPG key ID: 5CC908FDB71E12C2
29 changed files with 692 additions and 603 deletions
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47
lib/cf-https-connect.c
View file

@ -325,42 +325,25 @@ out:
return result;
}
static int cf_hc_get_select_socks(struct Curl_cfilter *cf,
static void cf_hc_adjust_pollset(struct Curl_cfilter *cf,
struct Curl_easy *data,
curl_socket_t *socks)
struct easy_pollset *ps)
{
struct cf_hc_ctx *ctx = cf->ctx;
size_t i, j, s;
int brc, rc = GETSOCK_BLANK;
curl_socket_t bsocks[MAX_SOCKSPEREASYHANDLE];
struct cf_hc_baller *ballers[2];
if(!cf->connected) {
struct cf_hc_ctx *ctx = cf->ctx;
struct cf_hc_baller *ballers[2];
size_t i;
if(cf->connected)
return cf->next->cft->get_select_socks(cf->next, data, socks);
ballers[0] = &ctx->h3_baller;
ballers[1] = &ctx->h21_baller;
for(i = s = 0; i < sizeof(ballers)/sizeof(ballers[0]); i++) {
struct cf_hc_baller *b = ballers[i];
if(!cf_hc_baller_is_active(b))
continue;
brc = Curl_conn_cf_get_select_socks(b->cf, data, bsocks);
CURL_TRC_CF(data, cf, "get_selected_socks(%s) -> %x", b->name, brc);
if(!brc)
continue;
for(j = 0; j < MAX_SOCKSPEREASYHANDLE && s < MAX_SOCKSPEREASYHANDLE; ++j) {
if((brc & GETSOCK_WRITESOCK(j)) || (brc & GETSOCK_READSOCK(j))) {
socks[s] = bsocks[j];
if(brc & GETSOCK_WRITESOCK(j))
rc |= GETSOCK_WRITESOCK(s);
if(brc & GETSOCK_READSOCK(j))
rc |= GETSOCK_READSOCK(s);
s++;
}
ballers[0] = &ctx->h3_baller;
ballers[1] = &ctx->h21_baller;
for(i = 0; i < sizeof(ballers)/sizeof(ballers[0]); i++) {
struct cf_hc_baller *b = ballers[i];
if(!cf_hc_baller_is_active(b))
continue;
Curl_conn_cf_adjust_pollset(b->cf, data, ps);
}
CURL_TRC_CF(data, cf, "adjust_pollset -> %d socks", ps->num);
}
CURL_TRC_CF(data, cf, "get_selected_socks -> %x", rc);
return rc;
}
static bool cf_hc_data_pending(struct Curl_cfilter *cf,
@ -455,7 +438,7 @@ struct Curl_cftype Curl_cft_http_connect = {
cf_hc_connect,
cf_hc_close,
Curl_cf_def_get_host,
cf_hc_get_select_socks,
cf_hc_adjust_pollset,
cf_hc_data_pending,
Curl_cf_def_send,
Curl_cf_def_recv,