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libevent-server: Use nghttp2_option_set_recv_client_preface()

This commit is contained in:
Tatsuhiro Tsujikawa 2014-09-13 19:58:39 +09:00
parent 901de5fbce
commit 5ff73de195
2 changed files with 72 additions and 104 deletions
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117
doc/sources/tutorial-server.rst
View File

@ -79,7 +79,6 @@ We use the ``http2_session_data`` structure to store session-level
app_context *app_ctx;
nghttp2_session *session;
char *client_addr;
size_t handshake_leftlen;
} http2_session_data;
We use the ``http2_stream_data`` structure to store stream-level data::
@ -91,17 +90,15 @@ We use the ``http2_stream_data`` structure to store stream-level data::
int fd;
} http2_stream_data;
A single HTTP/2 session can have multiple streams. We manage these multiple
streams with a doubly linked list. The first element of this list is pointed
to by the ``root->next`` in ``http2_session_data``. Initially, ``root->next``
is ``NULL``. The ``handshake_leftlen`` member of ``http2_session_data`` is
used to track the number of bytes remaining when receiving the first client
connection preface (:macro:`NGHTTP2_CLIENT_CONNECTION_PREFACE`), which is a 24
bytes long magic string from the client. We use libevent's bufferevent
structure to perform network I/O. Note that the bufferevent object is kept in
``http2_session_data`` and not in ``http2_stream_data``. This is because
``http2_stream_data`` is just a logical stream multiplexed over the single
connection managed by bufferevent in ``http2_session_data``.
A single HTTP/2 session can have multiple streams. We manage these
multiple streams with a doubly linked list. The first element of this
list is pointed to by the ``root->next`` in ``http2_session_data``.
Initially, ``root->next`` is ``NULL``. We use libevent's bufferevent
structure to perform network I/O. Note that the bufferevent object is
kept in ``http2_session_data`` and not in ``http2_stream_data``. This
is because ``http2_stream_data`` is just a logical stream multiplexed
over the single connection managed by bufferevent in
``http2_session_data``.
We first create a listener object to accept incoming connections. We use
libevent's ``struct evconnlistener`` for this purpose::
@ -148,13 +145,14 @@ accepted::
http2_session_data *session_data;
session_data = create_http2_session_data(app_ctx, fd, addr, addrlen);
bufferevent_setcb(session_data->bev, handshake_readcb, NULL, eventcb,
session_data);
bufferevent_setcb(session_data->bev, readcb, writecb, eventcb, session_data);
}
Here we create the ``http2_session_data`` object. The bufferevent for this
connection is also initialized at this time. We specify two callbacks for the
bufferevent: ``handshake_readcb`` and ``eventcb``.
Here we create the ``http2_session_data`` object. The bufferevent for
this connection is also initialized at this time. We specify three
callbacks for the bufferevent: ``readcb``, ``writecb`` and
``eventcb``.
The ``eventcb()`` callback is invoked by the libevent event loop when an event
(e.g., connection has been established, timeout, etc) happens on the
@ -165,6 +163,14 @@ underlying network socket::
http2_session_data *session_data = (http2_session_data*)ptr;
if(events & BEV_EVENT_CONNECTED) {
fprintf(stderr, "%s connected\n", session_data->client_addr);
initialize_nghttp2_session(session_data);
if(send_server_connection_header(session_data) != 0) {
delete_http2_session_data(session_data);
return;
}
return;
}
if(events & BEV_EVENT_EOF) {
@ -177,60 +183,29 @@ underlying network socket::
delete_http2_session_data(session_data);
}
For the ``BEV_EVENT_EOF``, ``BEV_EVENT_ERROR`` and ``BEV_EVENT_TIMEOUT``
events, we just simply tear down the connection. The
``delete_http2_session_data()`` function destroys the ``http2_session_data``
object and thus also its bufferevent member. As a result, the underlying
connection is closed. The ``BEV_EVENT_CONNECTED`` event is invoked when
SSL/TLS handshake is finished successfully.
``handshake_readcb()`` is a callback function to handle a 24 bytes magic byte
string coming from a client, since the nghttp2 library does not handle it::
static void handshake_readcb(struct bufferevent *bev, void *ptr)
{
http2_session_data *session_data = (http2_session_data*)ptr;
uint8_t data[24];
struct evbuffer *input = bufferevent_get_input(session_data->bev);
int readlen = evbuffer_remove(input, data, session_data->handshake_leftlen);
const char *conhead = NGHTTP2_CLIENT_CONNECTION_PREFACE;
if(memcmp(conhead + NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN
- session_data->handshake_leftlen, data, readlen) != 0) {
delete_http2_session_data(session_data);
return;
}
session_data->handshake_leftlen -= readlen;
if(session_data->handshake_leftlen == 0) {
bufferevent_setcb(session_data->bev, readcb, writecb, eventcb, ptr);
/* Process pending data in buffer since they are not notified
further */
initialize_nghttp2_session(session_data);
if(send_server_connection_header(session_data) != 0) {
delete_http2_session_data(session_data);
return;
}
if(session_recv(session_data) != 0) {
delete_http2_session_data(session_data);
return;
}
}
}
We check that the received byte string matches
:macro:`NGHTTP2_CLIENT_CONNECTION_PREFACE`. When they match, the connection
state is ready to start the HTTP/2 communication. First we change the callback
functions for the bufferevent object. We use the same ``eventcb`` callback as
before, but we specify new ``readcb`` and ``writecb`` functions to handle the
HTTP/2 communication. These two functions are described later.
For the ``BEV_EVENT_EOF``, ``BEV_EVENT_ERROR`` and
``BEV_EVENT_TIMEOUT`` events, we just simply tear down the connection.
The ``delete_http2_session_data()`` function destroys the
``http2_session_data`` object and thus also its bufferevent member.
As a result, the underlying connection is closed. The
``BEV_EVENT_CONNECTED`` event is invoked when SSL/TLS handshake is
finished successfully. Now we are ready to start the HTTP/2
communication.
We initialize a nghttp2 session object which is done in
``initialize_nghttp2_session()``::
static void initialize_nghttp2_session(http2_session_data *session_data)
{
nghttp2_option *option;
nghttp2_session_callbacks *callbacks;
nghttp2_option_new(&option);
/* Tells nghttp2_session object that it handles client connection
preface */
nghttp2_option_set_recv_client_preface(option, 1);
nghttp2_session_callbacks_new(&callbacks);
nghttp2_session_callbacks_set_send_callback(callbacks, send_callback);
@ -247,14 +222,22 @@ We initialize a nghttp2 session object which is done in
nghttp2_session_callbacks_set_on_begin_headers_callback
(callbacks, on_begin_headers_callback);
nghttp2_session_server_new(&session_data->session, callbacks, session_data);
nghttp2_session_server_new2(&session_data->session, callbacks, session_data,
option);
nghttp2_session_callbacks_del(callbacks);
nghttp2_option_del(option);
}
Since we are creating a server, the nghttp2 session object is created using
`nghttp2_session_server_new()` function. We registers five callbacks for
nghttp2 session object. We'll talk about these callbacks later.
Since we are creating a server and uses options, the nghttp2 session
object is created using `nghttp2_session_server_new2()` function. We
registers five callbacks for nghttp2 session object. We'll talk about
these callbacks later. Our server only speaks HTTP/2. In this case,
we use `nghttp2_option_set_recv_client_preface()` to make
:type:`nghttp2_session` object handle client connection preface, which
saves some lines of application code.
After initialization of the nghttp2 session object, we are going to send
a server connection header in ``send_server_connection_header()``::

59
examples/libevent-server.c
View File

@ -69,7 +69,6 @@ typedef struct http2_session_data {
app_context *app_ctx;
nghttp2_session *session;
char *client_addr;
size_t handshake_leftlen;
} http2_session_data;
struct app_context {
@ -192,7 +191,6 @@ static http2_session_data* create_http2_session_data(app_context *app_ctx,
(app_ctx->evbase, fd, ssl,
BUFFEREVENT_SSL_ACCEPTING,
BEV_OPT_CLOSE_ON_FREE | BEV_OPT_DEFER_CALLBACKS);
session_data->handshake_leftlen = NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN;
rv = getnameinfo(addr, addrlen, host, sizeof(host), NULL, 0, NI_NUMERICHOST);
if(rv != 0) {
session_data->client_addr = strdup("(unknown)");
@ -555,8 +553,15 @@ static int on_stream_close_callback(nghttp2_session *session,
static void initialize_nghttp2_session(http2_session_data *session_data)
{
nghttp2_option *option;
nghttp2_session_callbacks *callbacks;
nghttp2_option_new(&option);
/* Tells nghttp2_session object that it handles client connection
preface */
nghttp2_option_set_recv_client_preface(option, 1);
nghttp2_session_callbacks_new(&callbacks);
nghttp2_session_callbacks_set_send_callback(callbacks, send_callback);
@ -573,9 +578,13 @@ static void initialize_nghttp2_session(http2_session_data *session_data)
nghttp2_session_callbacks_set_on_begin_headers_callback
(callbacks, on_begin_headers_callback);
nghttp2_session_server_new(&session_data->session, callbacks, session_data);
nghttp2_session_server_new2(&session_data->session, callbacks, session_data,
option);
nghttp2_session_callbacks_del(callbacks);
nghttp2_option_del(option);
}
/* Send HTTP/2 client connection header, which includes 24 bytes
@ -638,6 +647,14 @@ static void eventcb(struct bufferevent *bev, short events, void *ptr)
http2_session_data *session_data = (http2_session_data*)ptr;
if(events & BEV_EVENT_CONNECTED) {
fprintf(stderr, "%s connected\n", session_data->client_addr);
initialize_nghttp2_session(session_data);
if(send_server_connection_header(session_data) != 0) {
delete_http2_session_data(session_data);
return;
}
return;
}
if(events & BEV_EVENT_EOF) {
@ -650,38 +667,6 @@ static void eventcb(struct bufferevent *bev, short events, void *ptr)
delete_http2_session_data(session_data);
}
/* readcb for bufferevent to check first 24 bytes client connection
header. */
static void handshake_readcb(struct bufferevent *bev, void *ptr)
{
http2_session_data *session_data = (http2_session_data*)ptr;
uint8_t data[24];
struct evbuffer *input = bufferevent_get_input(session_data->bev);
int readlen = evbuffer_remove(input, data, session_data->handshake_leftlen);
const char *conhead = NGHTTP2_CLIENT_CONNECTION_PREFACE;
if(memcmp(conhead + NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN
- session_data->handshake_leftlen, data, readlen) != 0) {
delete_http2_session_data(session_data);
return;
}
session_data->handshake_leftlen -= readlen;
if(session_data->handshake_leftlen == 0) {
bufferevent_setcb(session_data->bev, readcb, writecb, eventcb, ptr);
/* Process pending data in buffer since they are not notified
further */
initialize_nghttp2_session(session_data);
if(send_server_connection_header(session_data) != 0) {
delete_http2_session_data(session_data);
return;
}
if(session_recv(session_data) != 0) {
delete_http2_session_data(session_data);
return;
}
}
}
/* callback for evconnlistener */
static void acceptcb(struct evconnlistener *listener, int fd,
struct sockaddr *addr, int addrlen, void *arg)
@ -690,8 +675,8 @@ static void acceptcb(struct evconnlistener *listener, int fd,
http2_session_data *session_data;
session_data = create_http2_session_data(app_ctx, fd, addr, addrlen);
bufferevent_setcb(session_data->bev, handshake_readcb, NULL, eventcb,
session_data);
bufferevent_setcb(session_data->bev, readcb, writecb, eventcb, session_data);
}
static void start_listen(struct event_base *evbase, const char *service,