hio/lib/fcgi-cli.c

/*
    Copyright (c) 2016-2020 Chung, Hyung-Hwan. All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:
    1. Redistributions of source code must retain the above copyright
       notice, this list of conditions and the following disclaimer.
    2. Redistributions in binary form must reproduce the above copyright
       notice, this list of conditions and the following disclaimer in the
       documentation and/or other materials provided with the distribution.

    THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY EXPRESS OR
    IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
    IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
    NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
    THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <hio-fcgi.h>
#include <hio-sck.h>
#include "hio-prv.h"

struct hio_svc_fcgic_t
{
	HIO_SVC_HEADER;

	int stopping;
	int tmout_set;
	hio_svc_fcgic_tmout_t tmout;

	hio_svc_fcgic_conn_t* conns;
};

#if 0
#define CONN_SESS_CAPA_MAX (4)
#define CONN_SESS_INC  (2)
#else
#define CONN_SESS_CAPA_MAX (65536)
#define CONN_SESS_INC  (64)
#endif

struct hio_svc_fcgic_conn_t
{
	HIO_CFMB_HEADER;

	hio_svc_fcgic_t* fcgic;
	hio_skad_t addr;
	hio_dev_sck_t* dev;
	int connected;

	struct
	{
		hio_svc_fcgic_sess_t** ptr;
		hio_oow_t capa;
		hio_svc_fcgic_sess_t* free;
	} sess;

	struct
	{
		enum
		{
			R_AWAITING_HEADER,
			R_AWAITING_BODY
		} state;

		hio_uint8_t   type;
		hio_uint16_t  id;
		hio_uint16_t  content_len;
		hio_uint8_t   padding_len;

		hio_uint32_t body_len; /* content_len+ padding_len */
		hio_uint8_t buf[65792]; /* TODO: make it smaller by fireing on_read more frequently? */
		hio_oow_t len; /* current bufferred length */
	} r; /* space to parse incoming reply header */

	hio_svc_fcgic_conn_t* next;
};

struct fcgic_sck_xtn_t
{
	hio_svc_fcgic_conn_t* conn;
};
typedef struct fcgic_sck_xtn_t fcgic_sck_xtn_t;

static int make_connection_socket (hio_svc_fcgic_t* fcigc, hio_svc_fcgic_conn_t* conn);
static void release_session (hio_svc_fcgic_sess_t* sess);

static void sck_on_disconnect (hio_dev_sck_t* sck)
{
	fcgic_sck_xtn_t* sck_xtn = hio_dev_sck_getxtn(sck);
	hio_svc_fcgic_conn_t* conn = sck_xtn->conn;

printf ("DISCONNECT SOCKET .................. sck->%p conn->%p\n", sck, conn);

	if (conn)
	{
		hio_oow_t i;
		for (i = 0; i < conn->sess.capa; i++)
		{
			hio_svc_fcgic_sess_t* sess;
			sess = conn->sess.ptr[i];
			if (sess && sess->active)
			{
				release_session (sess); /* TODO: is this correct?? */
			}
		}
		conn->dev = HIO_NULL;
	}
}

static void sck_on_connect (hio_dev_sck_t* sck)
{
	fcgic_sck_xtn_t* sck_xtn = hio_dev_sck_getxtn(sck);
	hio_svc_fcgic_conn_t* conn = sck_xtn->conn;

printf ("FCGIC SOCKET CONNECTED >>>>>>>>>>>>>>>>>>>>>>>>>>\n");

	/* reinitialize the input parsing information */
	HIO_MEMSET (&conn->r, 0, HIO_SIZEOF(conn->r));
	conn->r.state = R_AWAITING_HEADER;

	if (conn->fcgic->tmout_set)
		hio_dev_sck_timedread (sck, 1, &conn->fcgic->tmout.r);
}

static int sck_on_write (hio_dev_sck_t* sck, hio_iolen_t wrlen, void* wrctx, const hio_skad_t* dstaddr)
{
	/* the lower 2 bits of the context is set to be the packet type in
	 *  hio_svc_fcgic_beginrequest()
	 *  hio_svc_fcgic_writeparam()
	 *  hio_svc_fcgic_writestdin()
	 */
	hio_svc_fcgic_sess_t* sess = (hio_svc_fcgic_sess_t*)((hio_oow_t)wrctx & ~(hio_oow_t)0x3);
	hio_oow_t type = ((hio_oow_t)wrctx & 0x3);
	static hio_fcgi_req_type_t rqtype[] =
	{
		HIO_FCGI_BEGIN_REQUEST,
		HIO_FCGI_PARAMS,
		HIO_FCGI_STDIN
	};

	if (wrlen > 0)
	{
		HIO_ASSERT (sess->conn->hio, wrlen >= HIO_SIZEOF(hio_fcgi_record_header_t));
		wrlen -= HIO_SIZEOF(hio_fcgi_record_header_t);
	}

	sess->on_write (sess, rqtype[type], wrlen, sess->ctx);
	return 0;
}

static int sck_on_read (hio_dev_sck_t* sck, const void* data, hio_iolen_t dlen, const hio_skad_t* srcaddr)
{
	fcgic_sck_xtn_t* sck_xtn = hio_dev_sck_getxtn(sck);
	hio_svc_fcgic_conn_t* conn = sck_xtn->conn;
	hio_t* hio = conn->fcgic->hio;

/*printf ("READ DATA FROM CGI SERVER %d\n", (int)dlen);*/
	if (dlen <= -1)
	{
		/* error or timeout */
/* fire all related fcgi sessions?? -> handled on disconnect */
		hio_dev_sck_halt (sck);
	}
	else if (dlen == 0)
	{
		/* EOF */
/* fire all related fcgi sessions?? -> handled on disconnect?? */
		hio_dev_sck_halt (sck);
	}
	else
	{
		do
		{
			hio_iolen_t reqlen, cplen;

			if (conn->r.state == R_AWAITING_HEADER)
			{
				hio_fcgi_record_header_t* h;

				HIO_ASSERT (hio, conn->r.len < HIO_SIZEOF(*h));

				reqlen = HIO_SIZEOF(*h) - conn->r.len;
				cplen = (dlen > reqlen)? reqlen: dlen;
				HIO_MEMCPY (&conn->r.buf[conn->r.len], data, cplen);
				conn->r.len += cplen;

				data += cplen;
				dlen -= cplen;

				if (conn->r.len < HIO_SIZEOF(*h))
				{
					/* not enough data to complete a header*/
					HIO_ASSERT (hio, dlen == 0);
					break;
				}

				/* header complted */
				h = (hio_fcgi_record_header_t*)conn->r.buf;
				conn->r.type = h->type;
				conn->r.id = hio_ntoh16(h->id);
				conn->r.content_len = hio_ntoh16(h->content_len);
				conn->r.padding_len = h->padding_len;

				conn->r.state = R_AWAITING_BODY;
				conn->r.body_len = conn->r.content_len + conn->r.padding_len;
				conn->r.len = 0; /* reset to 0 to use the buffer to hold body */

				/* the expected body length must not be too long */
				HIO_ASSERT (hio, conn->r.body_len <= HIO_SIZEOF(conn->r.buf)); 

				if (conn->r.type == HIO_FCGI_END_REQUEST && conn->r.content_len < HIO_SIZEOF(hio_fcgi_end_request_body_t))
				{
					/* invalid content_len encountered */
					/* TODO: logging*/
					hio_dev_sck_halt (sck);
					goto done;
				}

				if (conn->r.content_len == 0) goto got_body;
			}
			else /* R_AWAITING_BODY */
			{
				hio_svc_fcgic_sess_t* sess;

				reqlen = conn->r.body_len - conn->r.len;
				cplen = (dlen > reqlen)? reqlen: dlen;
				HIO_MEMCPY (&conn->r.buf[conn->r.len], data, cplen);
				conn->r.len += cplen;

				data += cplen;
				dlen -= cplen;

				if (conn->r.len < conn->r.body_len)
				{
					HIO_ASSERT (hio, dlen == 0);
					break;
				}

			got_body:
				/* get session by session id */
				sess = (conn->r.id >= 1 && conn->r.id <= conn->sess.capa)? conn->sess.ptr[conn->r.id - 1]: HIO_NULL;

				if (!sess || !sess->active)
				{
					/* discard the record. no associated sessoin or inactive session */
					goto back_to_header;
				}

				/* the complete body is in conn->r.buf */
				if (conn->r.type == HIO_FCGI_END_REQUEST)
				{
					hio_fcgi_end_request_body_t* erb = conn->r.buf;

					if (erb->proto_status != HIO_FCGI_REQUEST_COMPLETE)
					{
						/* error */
						hio_uint32_t app_status = hio_ntoh32(erb->app_status);
					}
					conn->r.content_len = 0; /* to indicate the end of input*/
				}
				else if (conn->r.content_len == 0 || conn->r.type != HIO_FCGI_STDOUT)
				{
					/* discard the record */
					/* TODO: log stderr to a file?? or handle it differently according to options given - discard or write to file */
					/* TODO: logging */
					goto back_to_header;
				}

				HIO_ASSERT (hio, conn->r.content_len <= conn->r.len);
				sess->on_read (sess, conn->r.buf, conn->r.content_len, sess->ctx); /* TODO: tell between stdout and stderr */

			back_to_header:
				conn->r.state = R_AWAITING_HEADER;
				conn->r.len = 0;
				conn->r.body_len = 0;
				conn->r.content_len = 0;
				conn->r.padding_len = 0;
			}
		} while (dlen > 0);
	}

done:
	return 0;
}

static int make_connection_socket (hio_svc_fcgic_t* fcgic, hio_svc_fcgic_conn_t* conn)
{
	hio_t* hio = conn->fcgic->hio;
	hio_dev_sck_t* sck;
	hio_dev_sck_make_t mi;
	hio_dev_sck_connect_t ci;
	fcgic_sck_xtn_t* sck_xtn;

	HIO_MEMSET (&mi, 0, HIO_SIZEOF(mi));
	if (hio_get_stream_sck_type_from_skad(&conn->addr, &mi.type) <= -1)
	{
		hio_seterrnum (hio, HIO_EINVAL);
		return -1;
	}
	mi.options = HIO_DEV_SCK_MAKE_LENIENT;
	mi.on_write = sck_on_write;
	mi.on_read = sck_on_read;
	mi.on_connect = sck_on_connect;
	mi.on_disconnect = sck_on_disconnect;

	sck = hio_dev_sck_make(hio, HIO_SIZEOF(*sck_xtn), &mi);
	if (HIO_UNLIKELY(!sck)) return -1;

	sck_xtn = hio_dev_sck_getxtn(sck);
	sck_xtn->conn = conn;

	HIO_MEMSET (&ci, 0, HIO_SIZEOF(ci));
	ci.remoteaddr = conn->addr;
	if (fcgic->tmout_set) ci.connect_tmout = fcgic->tmout.c;

	if (hio_dev_sck_connect(sck, &ci) <= -1)
	{
		/* immediate failure */
		sck_xtn->conn = HIO_NULL; /* disassociate the socket from the fcgi connection object */
		hio_dev_sck_halt (sck);
		return -1;
	}

	HIO_ASSERT (hio, conn->dev == HIO_NULL);
	conn->dev = sck;
	return 0;
}

static hio_svc_fcgic_conn_t* get_connection (hio_svc_fcgic_t* fcgic, const hio_skad_t* fcgis_addr)
{
	hio_t* hio = fcgic->hio;
	hio_svc_fcgic_conn_t* conn = fcgic->conns;

	/* TODO: speed up? how many conns would be configured? sequential search may be ok here */
	while (conn)
	{
		if (hio_equal_skads(&conn->addr, fcgis_addr, 1))
		{
			if (!conn->sess.free || conn->sess.capa <= (CONN_SESS_CAPA_MAX - CONN_SESS_INC))
			{
				/* the connection has room for more sessions */
				if (!conn->dev) make_connection_socket(fcgic, conn); /* conn->dev will still be null if connection fails*/
				return conn;
			}
		}
		conn = conn->next;
	}

	conn = hio_callocmem(hio, HIO_SIZEOF(*conn));
	if (HIO_UNLIKELY(!conn)) return HIO_NULL;

	conn->fcgic = fcgic;
	conn->addr = *fcgis_addr;
	conn->sess.capa = 0;
	conn->sess.free = HIO_NULL;

	if (make_connection_socket(fcgic, conn) <= -1)
	{
		hio_freemem (hio, conn);
		return HIO_NULL;
	}

	conn->next = fcgic->conns;
	fcgic->conns = conn;

	return conn;
}

static void destroy_connection_memory (hio_t* hio, hio_cfmb_t* cfmb)
{
	hio_svc_fcgic_conn_t* conn = (hio_svc_fcgic_conn_t*)cfmb;
	if (conn->sess.ptr) 
	{
		hio_oow_t i;

		/* destroy the session blocks allocated in new_session(). */
		for (i = 0; i < conn->sess.capa; i += CONN_SESS_INC)
			hio_freemem (hio, conn->sess.ptr[i]);

		/* destroy the session pointer bucket */
		hio_freemem (hio, conn->sess.ptr);
	}
	hio_freemem (hio, conn);
}

static void free_connections (hio_svc_fcgic_t* fcgic)
{
	hio_t* hio = fcgic->hio;
	hio_svc_fcgic_conn_t* conn = fcgic->conns;
	hio_svc_fcgic_conn_t* next;

	while (conn)
	{
		next = conn->next;
		if (conn->dev)
		{
			struct fcgic_sck_xtn_t* sck_xtn;
			sck_xtn = hio_dev_sck_getxtn(conn->dev);
			sck_xtn->conn = HIO_NULL;
			hio_dev_sck_halt (conn->dev);
		}

		/* delay destruction of conn->session.ptr and conn */
		hio_addcfmb (hio, (hio_cfmb_t*)conn, HIO_NULL, destroy_connection_memory);
		conn = next;
	}
}

static hio_svc_fcgic_sess_t* new_session (hio_svc_fcgic_t* fcgic, const hio_skad_t* fcgis_addr, hio_svc_fcgic_on_read_t on_read, hio_svc_fcgic_on_write_t on_write, hio_svc_fcgic_on_untie_t on_untie, void* ctx)
{
	hio_t* hio = fcgic->hio;
	hio_svc_fcgic_conn_t* conn;
	hio_svc_fcgic_sess_t* sess;

	conn = get_connection(fcgic, fcgis_addr);
	if (HIO_UNLIKELY(!conn)) return HIO_NULL;

	if (!conn->sess.free)
	{
		hio_oow_t newcapa, i;
		hio_svc_fcgic_sess_t** newptr;
		hio_svc_fcgic_sess_t* newblk;

		/* create a new session block */
		newblk = (hio_svc_fcgic_sess_t*)hio_callocmem(hio, HIO_SIZEOF(*sess) * CONN_SESS_INC);
		if (HIO_UNLIKELY(!newblk)) return HIO_NULL;

		/* reallocate the session pointer bucket */
		newcapa = conn->sess.capa + CONN_SESS_INC;
		newptr = (hio_svc_fcgic_sess_t**)hio_reallocmem(hio, conn->sess.ptr, HIO_SIZEOF(*newptr) * newcapa);
		if (HIO_UNLIKELY(!newptr)) 
		{
			hio_freemem (hio, newblk);
			return HIO_NULL;
		}

		for (i = 0; i < CONN_SESS_INC; i++)
		{
			/* management records use 0 for requestId.
			 * but application records have a nonzero requestId. */
			newptr[conn->sess.capa + i] = &newblk[i];
			newblk[i].sid = i + conn->sess.capa;
			newblk[i].conn = conn;
			newblk[i].active = 0;
			newblk[i].next = &newblk[i + 1];
		}
		newblk[i - 1].next = HIO_NULL;
		conn->sess.free = &newblk[0];
		conn->sess.capa = newcapa;
		conn->sess.ptr = newptr;
	}

	sess = conn->sess.free;
	conn->sess.free = sess->next;
	
	sess->on_read = on_read;
	sess->on_write = on_write;
	sess->on_untie = on_untie;
	sess->active = 1;
	sess->ctx = ctx;
	HIO_ASSERT (hio, sess->conn == conn);
	HIO_ASSERT (hio, sess->conn->fcgic == fcgic);

	return sess;
}

static void release_session (hio_svc_fcgic_sess_t* sess)
{
	if (sess->on_untie) sess->on_untie (sess, sess->ctx);
	sess->active = 0;
	sess->next = sess->conn->sess.free;
	sess->conn->sess.free = sess;
}

hio_svc_fcgic_t* hio_svc_fcgic_start (hio_t* hio, const hio_svc_fcgic_tmout_t* tmout)
{
	hio_svc_fcgic_t* fcgic = HIO_NULL;

	fcgic = (hio_svc_fcgic_t*)hio_callocmem(hio, HIO_SIZEOF(*fcgic));
	if (HIO_UNLIKELY(!fcgic)) goto oops;

	fcgic->hio = hio;
	fcgic->svc_stop = (hio_svc_stop_t)hio_svc_fcgic_stop;

	if (tmout)
	{
		fcgic->tmout = *tmout;
		fcgic->tmout_set = 1;
	}

	HIO_SVCL_APPEND_SVC (&hio->actsvc, (hio_svc_t*)fcgic);
	HIO_DEBUG1 (hio, "FCGIC - STARTED SERVICE %p\n", fcgic);
	return fcgic;

oops:
	if (fcgic) hio_freemem (hio, fcgic);
	return HIO_NULL;
}

void hio_svc_fcgic_stop (hio_svc_fcgic_t* fcgic)
{
	hio_t* hio = fcgic->hio;

	HIO_DEBUG1 (hio, "FCGIC - STOPPING SERVICE %p\n", fcgic);
	fcgic->stopping = 1;

	free_connections (fcgic);

	HIO_SVCL_UNLINK_SVC (fcgic);
	hio_freemem (hio, fcgic);

	HIO_DEBUG1 (hio, "FCGIC - STOPPED SERVICE %p\n", fcgic);
}

hio_svc_fcgic_sess_t* hio_svc_fcgic_tie (hio_svc_fcgic_t* fcgic, const hio_skad_t* addr, hio_svc_fcgic_on_read_t on_read, hio_svc_fcgic_on_write_t on_write, hio_svc_fcgic_on_untie_t on_untie, void* ctx)
{
	/* TODO: reference counting for safety?? */
	return new_session(fcgic, addr, on_read, on_write, on_untie, ctx);
}

void hio_svc_fcgic_untie (hio_svc_fcgic_sess_t* sess)
{
	/* TODO: reference counting for safety?? */
	release_session (sess);
}

int hio_svc_fcgic_beginrequest (hio_svc_fcgic_sess_t* sess)
{
	hio_svc_fcgic_conn_t* conn = sess->conn;
	hio_t* hio = conn->hio;
	hio_iovec_t iov[2];
	hio_fcgi_record_header_t h;
	hio_fcgi_begin_request_body_t b;
	void* wrctx;

	if (!sess->conn->dev)
	{
		hio_seterrbfmt (hio, HIO_EPERM, "fcgi not connected");
		return -1;
	}

	HIO_MEMSET (&h, 0, HIO_SIZEOF(h));
	h.version = HIO_FCGI_VERSION;
	h.type = HIO_FCGI_BEGIN_REQUEST;
	/* management records use 0 for requestId.
	 * but application records have a nonzero requestId. */
	h.id = hio_hton16(sess->sid + 1);
	h.content_len = hio_hton16(HIO_SIZEOF(b));
	h.padding_len = 0;

	HIO_MEMSET (&b, 0, HIO_SIZEOF(b));
	b.role = HIO_CONST_HTON16(HIO_FCGI_ROLE_RESPONDER);
	b.flags = HIO_FCGI_KEEP_CONN;

	iov[0].iov_ptr = &h;
	iov[0].iov_len = HIO_SIZEOF(h);
	iov[1].iov_ptr = &b;
	iov[1].iov_len = HIO_SIZEOF(b);

	HIO_ASSERT (sess->conn->hio, ((hio_oow_t)sess & 3) == 0);
	wrctx = ((hio_oow_t)sess | 0);  /* see the sck_on_write()  */
	return hio_dev_sck_writev(sess->conn->dev, iov, 2, wrctx, HIO_NULL);
}

int hio_svc_fcgic_writeparam (hio_svc_fcgic_sess_t* sess, const void* key, hio_iolen_t ksz, const void* val, hio_iolen_t vsz)
{
	hio_svc_fcgic_conn_t* conn = sess->conn;
	hio_t* hio = conn->hio;
	hio_iovec_t iov[4];
	hio_fcgi_record_header_t h;
	hio_uint8_t sz[8];
	hio_oow_t szc = 0;
	hio_oow_t plen = 0;
	void* wrctx;

	if (!conn->dev)
	{
		hio_seterrbfmt (hio, HIO_EPERM, "fcgi not connected");
		return -1;
	}

	/* TODO: check ksz and vsz can't exceed max 32bit value. */
	/* limit sizes to the max of the signed 32-bit interger
	*  the high-order bit is used as encoding marker (1-byte or 4-byte encoding).
	*  so a size can't hit the unsigned max. */
	ksz &= HIO_TYPE_MAX(hio_int32_t);
	vsz &= HIO_TYPE_MAX(hio_int32_t);

	if (ksz > 0)
	{
		if (ksz > 0x7F)
		{
			sz[szc++] = (ksz >> 24) | 0x80;
			sz[szc++] = (ksz >> 16) & 0xFF;
			sz[szc++] = (ksz >> 8) & 0xFF;
			sz[szc++] = ksz & 0xFF;
		}
		else
		{
			sz[szc++] = ksz;
		}

		if (vsz > 0x7F)
		{
			sz[szc++] = (vsz >> 24) | 0x80;
			sz[szc++] = (vsz >> 16) & 0xFF;
			sz[szc++] = (vsz >> 8) & 0xFF;
			sz[szc++] = vsz & 0xFF;
		}
		else
		{
			sz[szc++] = vsz;
		}

		plen = szc + ksz + vsz;
		if (plen > 0xFFFF)
		{
			hio_seterrbfmt (hio, HIO_EINVAL, "fcgi parameter too large");
			return -1;
		}
	}

	HIO_MEMSET (&h, 0, HIO_SIZEOF(h));
	h.version = HIO_FCGI_VERSION;
	h.type = HIO_FCGI_PARAMS;
	h.id = hio_hton16(sess->sid + 1);
	h.content_len = hio_hton16(plen);
	h.padding_len = 0;

	iov[0].iov_ptr = &h;
	iov[0].iov_len = HIO_SIZEOF(h);
	if (ksz > 0)
	{
		iov[1].iov_ptr = sz;
		iov[1].iov_len = szc;
		iov[2].iov_ptr = key;
		iov[2].iov_len = ksz;
		iov[3].iov_ptr = val;
		iov[3].iov_len = vsz;
	}

	HIO_ASSERT (sess->conn->hio, ((hio_oow_t)sess & 3) == 0);
	wrctx = ((hio_oow_t)sess | 1);  /* see the sck_on_write()  */
	return hio_dev_sck_writev(sess->conn->dev, iov, (ksz > 0? 4: 1), wrctx, HIO_NULL);
}

int hio_svc_fcgic_writestdin (hio_svc_fcgic_sess_t* sess, const void* data, hio_iolen_t size)
{
	hio_svc_fcgic_conn_t* conn = sess->conn;
	hio_t* hio = conn->hio;
	hio_iovec_t iov[2];
	hio_fcgi_record_header_t h;
	void* wrctx;

	if (!sess->conn->dev)
	{
		hio_seterrbfmt (hio, HIO_EPERM, "fcgi not connected");
		return -1;
	}

	HIO_MEMSET (&h, 0, HIO_SIZEOF(h));
	h.version = HIO_FCGI_VERSION;
	h.type = HIO_FCGI_STDIN;
	h.id = hio_hton16(sess->sid + 1);
	h.content_len = hio_hton16(size);

	iov[0].iov_ptr = &h;
	iov[0].iov_len = HIO_SIZEOF(h);
	if (size > 0)
	{
		iov[1].iov_ptr = (void*)data;
		iov[1].iov_len = size;
	}

	HIO_ASSERT (sess->conn->hio, ((hio_oow_t)sess & 3) == 0);
	wrctx = ((hio_oow_t)sess | 2);  /* see the sck_on_write()  */
	return hio_dev_sck_writev(sess->conn->dev, iov, (size > 0? 2: 1), wrctx, HIO_NULL);
}