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introduce LWS_CALLBACK_CLIENT_APPEND_HANDSHAKE_HEADER

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This adds a callback to protocols[0] which happens when the
Client HTTP handshake packet is being composed.  After all the
headers for the websocket handshake to the server have been
added, the callback is called with a pointer to a char *
that allows extra headers to be added.  See the comments in
libwebsocket.h or the api documentation for example code.

Signed-off-by: Andy Green <andy@warmcat.com>
This commit is contained in:
Andy Green 2011-03-01 21:06:02 +00:00
parent eeaacb39c7
commit 385e7ad034
3 changed files with 66 additions and 1 deletions
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16
lib/libwebsockets.c
View file

@ -900,6 +900,12 @@ libwebsocket_service_fd(struct libwebsocket_context *this,
p += sprintf(p, "Sec-WebSocket-Key2: %s\x0d\x0a",
key_2);
/* give userland a chance to append, eg, cookies */
this->protocols[0].callback(this, wsi,
LWS_CALLBACK_CLIENT_APPEND_HANDSHAKE_HEADER,
NULL, &p, (pkt + sizeof(pkt)) - p - 12);
p += sprintf(p, "\x0d\x0a");
read(this->fd_random, p, 8);
@ -927,9 +933,17 @@ libwebsocket_service_fd(struct libwebsocket_context *this,
if (wsi->c_protocol)
p += sprintf(p, "Sec-WebSocket-Protocol: %s\x0d\x0a",
wsi->c_protocol);
p += sprintf(p, "Sec-WebSocket-Version: %d\x0d\x0a\x0d\x0a",
p += sprintf(p, "Sec-WebSocket-Version: %d\x0d\x0a",
wsi->ietf_spec_revision);
/* give userland a chance to append, eg, cookies */
this->protocols[0].callback(this, wsi,
LWS_CALLBACK_CLIENT_APPEND_HANDSHAKE_HEADER,
NULL, &p, (pkt + sizeof(pkt)) - p - 12);
p += sprintf(p, "\x0d\x0a");
/* prepare the expected server accept response */
strcpy((char *)buf, wsi->key_b64);

25
lib/libwebsockets.h
View file

@ -47,6 +47,7 @@ enum libwebsocket_callback_reasons {
LWS_CALLBACK_OPENSSL_LOAD_EXTRA_CLIENT_VERIFY_CERTS,
LWS_CALLBACK_OPENSSL_LOAD_EXTRA_SERVER_VERIFY_CERTS,
LWS_CALLBACK_OPENSSL_PERFORM_CLIENT_CERT_VERIFICATION,
LWS_CALLBACK_CLIENT_APPEND_HANDSHAKE_HEADER,
/* external poll() management support */
LWS_CALLBACK_ADD_POLL_FD,
@ -276,6 +277,30 @@ struct libwebsocket_context;
* the default callback action of returning 0 allows the client
* certificates.
*
* LWS_CALLBACK_CLIENT_APPEND_HANDSHAKE_HEADER: this callback happens
* when a client handshake is being compiled. @user is NULL,
* @in is a char **, it's pointing to a char * which holds the
* next location in the header buffer where you can add
* headers, and @len is the remaining space in the header buffer,
* which is typically some hundreds of bytes. So, to add a canned
* cookie, your handler code might look similar to:
*
* char **p = (char **)in;
*
* if (len < 100)
* return 1;
*
* *p += sprintf(*p, "Cookie: a=b\x0d\x0a");
*
* return 0;
*
* Notice if you add anything, you just have to take care about
* the CRLF on the line you added. Obviously this callback is
* optional, if you don't handle it everything is fine.
*
* Notice the callback is coming to protocols[0] all the time,
* because there is no specific protocol handshook yet.
*
* The next four reasons are optional and only need taking care of if you
* will be integrating libwebsockets sockets into an external polling
* array.

26
libwebsockets-api-doc.html
View file

@ -621,6 +621,32 @@ conventions, return 0 to mean the cert is OK or 1 to fail it.
This also means that if you don't handle this callback then
the default callback action of returning 0 allows the client
certificates.
</blockquote>
<h3>LWS_CALLBACK_CLIENT_APPEND_HANDSHAKE_HEADER</h3>
<blockquote>
this callback happens
when a client handshake is being compiled. <tt><b>user</b></tt> is NULL,
<tt><b>in</b></tt> is a char **, it's pointing to a char * which holds the
next location in the header buffer where you can add
headers, and <tt><b>len</b></tt> is the remaining space in the header buffer,
which is typically some hundreds of bytes. So, to add a canned
cookie, your handler code might look similar to:
<p>
char **p = (char **)in;
<p>
if (len &lt; 100)
return 1;
<p>
*p += sprintf(*p, "Cookie: a=b\x0d\x0a");
<p>
return 0;
<p>
Notice if you add anything, you just have to take care about
the CRLF on the line you added. Obviously this callback is
optional, if you don't handle it everything is fine.
<p>
Notice the callback is coming to protocols[0] all the time,
because there is no specific protocol handshook yet.
<p>
The next four reasons are optional and only need taking care of if you
will be integrating libwebsockets sockets into an external polling