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api: comment, simplify and fix api socket read

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The function vl_socket_read_ready did contain some comments already,
but as they stated, the logic has to be tricky to cover multiple cases.

Comment:
+ Add function-level comment
+ Add comments to describe some of local variables
+ Add many comments to describe internal state at particular lines.

Simplify:
+ Remov mbp_set as it is never needed.
+ Replace msg_len with msgbuf_len to save "+ sizeof (msgbuf_t)".

Improve:
+ Early exit on EAGAIN.

Fix:
+ "n" now only tracks input_buffer.
  Previously, it was entering the detection of additional messages
  even for unprocessed_input.
+ Set up msg_buffer (including appending to unprocessed_input)
  outside full-message-detection loop now,
  so it cannot be executed multiple times as before.

Type: fix
Ticket: VPP-1785

Change-Id: I256e34b435be06844458744a13ea37a0e86a96f9
Signed-off-by: Vratko Polak <vrpolak@cisco.com>
(cherry picked from commit 6a6af6ea1a)
This commit is contained in:
Vratko Polak
2019-10-07 14:52:53 +02:00
committed by Dave Barach
parent 05c2f5b73e
commit 72ab26ca8f
1 changed files with 78 additions and 46 deletions
Download Patch File Download Diff File Expand all files Collapse all files

124
src/vlibmemory/socket_api.c
View File

@ -203,43 +203,68 @@ vl_socket_process_api_msg (clib_file_t * uf, vl_api_registration_t * rp,
socket_main.current_rp = 0;
}
/*
* Read function for API socket.
*
* Read data from socket, invoke SOCKET_READ_EVENT
* for each fully read API message, return 0.
* Store incomplete data for next invocation to continue.
*
* On severe read error, the file is closed.
*
* As reading is single threaded,
* socket_main.input_buffer is used temporarily.
* Even its length is modified, but always restored before return.
*
* Incomplete data is copied into a vector,
* pointer saved in registration's unprocessed_input.
*/
clib_error_t *
vl_socket_read_ready (clib_file_t * uf)
{
clib_file_main_t *fm = &file_main;
vlib_main_t *vm = vlib_get_main ();
vl_api_registration_t *rp;
/* n is the size of data read to input_buffer */
int n;
/* msg_buffer vector can point to input_buffer or unprocessed_input */
i8 *msg_buffer = 0;
/* data_for_process is a vector containing one full message, incl msgbuf_t */
u8 *data_for_process;
u32 msg_len;
/* msgbuf_len is the size of one message, including sizeof (msgbuf_t) */
u32 msgbuf_len;
u32 save_input_buffer_length = vec_len (socket_main.input_buffer);
vl_socket_args_for_process_t *a;
msgbuf_t *mbp;
int mbp_set = 0;
rp = pool_elt_at_index (socket_main.registration_pool, uf->private_data);
/* Ignore unprocessed_input for now, n describes input_buffer for now. */
n = read (uf->file_descriptor, socket_main.input_buffer,
vec_len (socket_main.input_buffer));
if (n <= 0 && errno != EAGAIN)
if (n <= 0)
{
clib_file_del (fm, uf);
if (errno != EAGAIN)
{
/* Severe error, close the file. */
clib_file_del (fm, uf);
if (!pool_is_free (socket_main.registration_pool, rp))
{
u32 index = rp - socket_main.registration_pool;
vl_socket_free_registration_index (index);
}
else
{
clib_warning ("client index %d already free?",
rp->vl_api_registration_pool_index);
if (!pool_is_free (socket_main.registration_pool, rp))
{
u32 index = rp - socket_main.registration_pool;
vl_socket_free_registration_index (index);
}
else
{
clib_warning ("client index %d already free?",
rp->vl_api_registration_pool_index);
}
}
/* EAGAIN means we do not close the file, but no data to process anyway. */
return 0;
}
/* Fake smaller length teporarily, so input_buffer can be used as msg_buffer. */
_vec_len (socket_main.input_buffer) = n;
/*
@ -248,37 +273,38 @@ vl_socket_read_ready (clib_file_t * uf)
* boundaries. In the case of a long message (>4K bytes)
* we have to do (at least) 2 reads, etc.
*/
/* Determine msg_buffer. */
if (vec_len (rp->unprocessed_input))
{
vec_append (rp->unprocessed_input, socket_main.input_buffer);
msg_buffer = rp->unprocessed_input;
}
else
{
msg_buffer = socket_main.input_buffer;
}
/* Loop to process any full messages. */
ASSERT (vec_len (msg_buffer) > 0);
do
{
if (vec_len (rp->unprocessed_input))
{
vec_append (rp->unprocessed_input, socket_main.input_buffer);
msg_buffer = rp->unprocessed_input;
}
else
{
msg_buffer = socket_main.input_buffer;
mbp_set = 0;
}
/* Here, we are not sure how big a chunk of message we have left. */
/* Do we at least know how big the full message will be? */
if (vec_len (msg_buffer) <= sizeof (msgbuf_t))
/* No, so fragment is not a full message. */
goto save_and_split;
if (mbp_set == 0)
{
/* Any chance that we have a complete message? */
if (vec_len (msg_buffer) <= sizeof (msgbuf_t))
goto save_and_split;
/* Now we know how big the full message will be. */
msgbuf_len =
ntohl (((msgbuf_t *) msg_buffer)->data_len) + sizeof (msgbuf_t);
mbp = (msgbuf_t *) msg_buffer;
msg_len = ntohl (mbp->data_len);
mbp_set = 1;
}
/* We don't have the entire message yet. */
if (mbp_set == 0
|| (msg_len + sizeof (msgbuf_t)) > vec_len (msg_buffer))
/* But do we have a full message? */
if (msgbuf_len > vec_len (msg_buffer))
{
save_and_split:
/* if we were using the input buffer save the fragment */
/* We don't have the entire message yet. */
/* If msg_buffer is unprocessed_input, nothing needs to be done. */
if (msg_buffer == socket_main.input_buffer)
/* But if we were using the input buffer, save the fragment. */
{
ASSERT (vec_len (rp->unprocessed_input) == 0);
vec_validate (rp->unprocessed_input, vec_len (msg_buffer) - 1);
@ -286,12 +312,19 @@ vl_socket_read_ready (clib_file_t * uf)
vec_len (msg_buffer));
_vec_len (rp->unprocessed_input) = vec_len (msg_buffer);
}
/* No more full messages, restore original input_buffer length. */
_vec_len (socket_main.input_buffer) = save_input_buffer_length;
return 0;
}
/*
* We have at least one full message.
* But msg_buffer can contain more data, so copy one message data
* so we can overwrite its length to what single message has.
*/
data_for_process = (u8 *) vec_dup (msg_buffer);
_vec_len (data_for_process) = (msg_len + sizeof (msgbuf_t));
_vec_len (data_for_process) = msgbuf_len;
/* Everything is ready to signal the SOCKET_READ_EVENT. */
pool_get (socket_main.process_args, a);
a->clib_file = uf;
a->regp = rp;
@ -300,18 +333,17 @@ vl_socket_read_ready (clib_file_t * uf)
vlib_process_signal_event (vm, vl_api_clnt_node.index,
SOCKET_READ_EVENT,
a - socket_main.process_args);
if (n > (msg_len + sizeof (*mbp)))
vec_delete (msg_buffer, msg_len + sizeof (*mbp), 0);
if (vec_len (msg_buffer) > msgbuf_len)
/* There are some fragments left. Shrink the msg_buffer to simplify logic. */
vec_delete (msg_buffer, msgbuf_len, 0);
else
/* We are done with msg_buffer. */
_vec_len (msg_buffer) = 0;
n -= msg_len + sizeof (msgbuf_t);
msg_len = 0;
mbp_set = 0;
}
while (n > 0);
while (vec_len (msg_buffer) > 0);
/* Restore input_buffer, it could have been msg_buffer. */
_vec_len (socket_main.input_buffer) = save_input_buffer_length;
return 0;
}