[PATCH 1 of 3] QUIC: introduced explicit stream states

[Vladimir Homutov]

On Mon, Jan 31, 2022 at 10:34:06AM +0300, Roman Arutyunyan wrote:
> # HG changeset patch
> # User Roman Arutyunyan <arut at nginx.com>
> # Date 1643611562 -10800
> #      Mon Jan 31 09:46:02 2022 +0300
> # Branch quic
> # Node ID 8dcb9908989401d750b14fe5dccf444a5485c23d
> # Parent  81a3429db8b00ec9fc476d3687d1cd18088f3365
> QUIC: introduced explicit stream states.
>
> This allows to eliminate the usage of stream connection event flags for tracking
> stream state.
>
> diff --git a/src/event/quic/ngx_event_quic.h b/src/event/quic/ngx_event_quic.h
> --- a/src/event/quic/ngx_event_quic.h
> +++ b/src/event/quic/ngx_event_quic.h
> @@ -28,6 +28,26 @@
>  #define NGX_QUIC_STREAM_UNIDIRECTIONAL       0x02
>
>
> +typedef enum {
> +    NGX_QUIC_STREAM_SEND_READY = 0,
> +    NGX_QUIC_STREAM_SEND_SEND,
> +    NGX_QUIC_STREAM_SEND_DATA_SENT,
> +    NGX_QUIC_STREAM_SEND_DATA_RECVD,
> +    NGX_QUIC_STREAM_SEND_RESET_SENT,
> +    NGX_QUIC_STREAM_SEND_RESET_RECVD
> +} ngx_quic_stream_send_state_e;
> +
> +
> +typedef enum {
> +    NGX_QUIC_STREAM_RECV_RECV = 0,
> +    NGX_QUIC_STREAM_RECV_SIZE_KNOWN,
> +    NGX_QUIC_STREAM_RECV_DATA_RECVD,
> +    NGX_QUIC_STREAM_RECV_DATA_READ,
> +    NGX_QUIC_STREAM_RECV_RESET_RECVD,
> +    NGX_QUIC_STREAM_RECV_RESET_READ
> +} ngx_quic_stream_recv_state_e;
> +
> +
>  typedef struct {
>      ngx_ssl_t                 *ssl;
>
> @@ -66,6 +86,8 @@ struct ngx_quic_stream_s {
>      ngx_chain_t               *in;
>      ngx_chain_t               *out;
>      ngx_uint_t                 cancelable;  /* unsigned  cancelable:1; */
> +    ngx_quic_stream_send_state_e  send_state;
> +    ngx_quic_stream_recv_state_e  recv_state;
>  };

let's fix this little style incosistency in a separate patch by moving
all struct stuff to the right.

[..]

> @@ -780,8 +764,23 @@ ngx_quic_stream_recv(ngx_connection_t *c
>
>      ngx_quic_free_chain(pc, in);
>
> -    if (qs->in == NULL) {
> -        rev->ready = rev->pending_eof;
> +    if (len == 0) {

this also covers the case when ngx_quic_stream_recv() is called
with zero-length buffer. Not sure what semantic should be implemented.

man 2 read says:

    If count is zero, read() may detect the errors described below.  In
    the absence of any errors, or if read() does not check for errors, a
    read()  with a count of 0 returns zero and has no other effects.

i.e. if we have data in buffer, but we are called with zero, we should
not change state probably and handle this case separately.

> +        rev->ready = 0;
> +
> +        if (qs->recv_state == NGX_QUIC_STREAM_RECV_SIZE_KNOWN
> +            && qs->recv_offset == qs->final_size)
> +        {
> +            qs->recv_state = NGX_QUIC_STREAM_RECV_DATA_READ;
> +        }
> +
> +        if (qs->recv_state == NGX_QUIC_STREAM_RECV_DATA_READ) {
> +            rev->eof = 1;
> +            return 0;
> +        }
> +
> +        ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0,
> +                       "quic stream id:0x%xL recv() not ready", qs->id);
> +        return NGX_AGAIN;
>      }
>
>      ngx_log_debug2(NGX_LOG_DEBUG_EVENT, c->log, 0,


side note:  while looking at state transitions, i've realized we never send
STREAM_DATA_BLOCKED and DATA_BLOCKED.