docs: networking: strparser: remove general mode

Now that the general mode of strp has been removed from the code,
update the documentation.

Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://patch.msgid.link/0a31a783d4c9c38594da338c49bf085fe6336c92.1790702233.git.sd@queasysnail.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/networking/strparser.rst

@@ -8,32 +8,24 @@ Introduction
 ============
 
 The stream parser (strparser) is a utility that parses messages of an
-application layer protocol running over a data stream. The stream
+application layer protocol running over a TCP connection. The stream
 parser works in conjunction with an upper layer in the kernel to provide
 kernel support for application layer messages. For instance, Kernel
 Connection Multiplexor (KCM) uses the Stream Parser to parse messages
 using a BPF program.
 
-The strparser works in one of two modes: receive callback or general
+The strparser is called from the data_ready callback of a TCP
-mode.
+socket. Messages are parsed and delivered as they are received on the
-
+socket.
-In receive callback mode, the strparser is called from the data_ready
-callback of a TCP socket. Messages are parsed and delivered as they are
-received on the socket.
-
-In general mode, a sequence of skbs are fed to strparser from an
-outside source. Message are parsed and delivered as the sequence is
-processed. This modes allows strparser to be applied to arbitrary
-streams of data.
 
 Interface
 =========
 
 The API includes a context structure, a set of callbacks, utility
-functions, and a data_ready function for receive callback mode. The
+functions, and a data_ready function. The callbacks include a
-callbacks include a parse_msg function that is called to perform
+parse_msg function that is called to perform parsing (e.g. BPF parsing
-parsing (e.g.  BPF parsing in case of KCM), and a rcv_msg function
+in case of KCM), and a rcv_msg function that is called when a full
-that is called when a full message has been completed.
+message has been completed.
 
 Functions
 =========
@@ -45,9 +37,8 @@ Functions
 
      Called to initialize a stream parser. strp is a struct of type
      strparser that is allocated by the upper layer. sk is the TCP
-     socket associated with the stream parser for use with receive
+     socket associated with the stream parser. Callbacks are called by
-     callback mode; in general mode this is set to NULL. Callbacks
+     the stream parser (the callbacks are listed below).
-     are called by the stream parser (the callbacks are listed below).
 
      ::
 
@@ -79,18 +70,6 @@ Functions
      parser instance. This must be called after the stream processor
      has been stopped.
 
-     ::
-
-	int strp_process(struct strparser *strp, struct sk_buff *orig_skb,
-			 unsigned int orig_offset, size_t orig_len,
-			 size_t max_msg_size, long timeo)
-
-    strp_process is called in general mode for a stream parser to
-    parse an sk_buff. The number of bytes processed or a negative
-    error number is returned. Note that strp_process does not
-    consume the sk_buff. max_msg_size is maximum size the stream
-    parser will parse. timeo is timeout for completing a message.
-
     ::
 
 	void strp_data_ready(struct strparser *strp);
@@ -112,16 +91,15 @@ Functions
 Callbacks
 =========
 
-There are seven callbacks:
+There are four callbacks:
 
     ::
 
 	int (*parse_msg)(struct strparser *strp, struct sk_buff *skb);
 
-    parse_msg is called to determine the length of the next message
+    parse_msg is called to determine the length of the next message in
-    in the stream. The upper layer must implement this function. It
+    the stream. It should parse the sk_buff as containing the headers
-    should parse the sk_buff as containing the headers for the
+    for the next application layer message in the stream.
-    next application layer message in the stream.
 
     The strparser metadata in the input skb can be accessed with
     strp_msg(skb). Only the offset field is relevant in parse_msg and
@@ -141,30 +119,13 @@ There are seven callbacks:
     =========    ===========================================================
 
     In the case that an error is returned (return value is less than
-    zero) and the parser is in receive callback mode, then it will set
+    zero), it will set the error on TCP socket and wake it up. If
-    the error on TCP socket and wake it up. If parse_msg returned
+    parse_msg returned -ESTRPIPE and the stream parser had previously
-    -ESTRPIPE and the stream parser had previously read some bytes for
+    read some bytes for the current message, then the error set on the
-    the current message, then the error set on the attached socket is
+    attached socket is ENODATA since the stream is unrecoverable in
-    ENODATA since the stream is unrecoverable in that case.
+    that case.
 
-    ::
+    This callback must be set.
-
-	void (*lock)(struct strparser *strp)
-
-    The lock callback is called to lock the strp structure when
-    the strparser is performing an asynchronous operation (such as
-    processing a timeout). In receive callback mode the default
-    function is to lock_sock for the associated socket. In general
-    mode the callback must be set appropriately.
-
-    ::
-
-	void (*unlock)(struct strparser *strp)
-
-    The unlock callback is called to release the lock obtained
-    by the lock callback. In receive callback mode the default
-    function is release_sock for the associated socket. In general
-    mode the callback must be set appropriately.
 
     ::
 
@@ -173,8 +134,7 @@ There are seven callbacks:
     rcv_msg is called when a full message has been received and
     is queued. The callee must consume the sk_buff; it can
     call strp_pause to prevent any further messages from being
-    received in rcv_msg (see strp_pause above). This callback
+    received in rcv_msg (see strp_pause above).
-    must be set.
 
     The strparser metadata in the input skb can be accessed with
     strp_msg(skb). This struct contains two fields: offset and full_len.
@@ -182,6 +142,8 @@ There are seven callbacks:
     the length of the message. skb->len - offset may be greater than
     full_len since strparser does not trim the skb.
 
+    This callback must be set.
+
     ::
 
 	int (*read_sock)(struct strparser *strp, read_descriptor_t *desc,
@@ -189,25 +151,20 @@ There are seven callbacks:
 
     The read_sock callback is used by strparser instead of
     sock->ops->read_sock, if provided.
+
+    This callback is optional.
+
     ::
 
 	int (*read_sock_done)(struct strparser *strp, int err);
 
      read_sock_done is called when the stream parser is done reading
-     the TCP socket in receive callback mode. The stream parser may
+     the TCP socket. The stream parser may read multiple messages in a
-     read multiple messages in a loop and this function allows cleanup
+     loop and this function allows cleanup to occur when exiting the
-     to occur when exiting the loop. If the callback is not set (NULL
+     loop. If the callback is not set (NULL in strp_init) a default
-     in strp_init) a default function is used.
+     function is used.
 
-     ::
+    This callback is optional.
-
-	void (*abort_parser)(struct strparser *strp, int err);
-
-     This function is called when stream parser encounters an error
-     in parsing. The default function stops the stream parser and
-     sets the error in the socket if the parser is in receive callback
-     mode. The default function can be changed by setting the callback
-     to non-NULL in strp_init.
 
 Statistics
 ==========
@@ -224,23 +181,18 @@ Message assembly limits
 The stream parser provide mechanisms to limit the resources consumed by
 message assembly.
 
-A timer is set when assembly starts for a new message. In receive
+A timer is set when assembly starts for a new message. The message
-callback mode the message timeout is taken from rcvtime for the
+timeout is taken from rcvtime for the associated TCP socket. If the
-associated TCP socket. In general mode, the timeout is passed as an
+timer fires before assembly completes the stream parser is aborted and
-argument in strp_process. If the timer fires before assembly completes
+the ETIMEDOUT error is set on the TCP socket.
-the stream parser is aborted and the ETIMEDOUT error is set on the TCP
-socket if in receive callback mode.
 
-In receive callback mode, message length is limited to the receive
+Message length is limited to the receive
 buffer size of the associated TCP socket. If the length returned by
 parse_msg is greater than the socket buffer size then the stream parser
 is aborted with EMSGSIZE error set on the TCP socket. Note that this
 makes the maximum size of receive skbuffs for a socket with a stream
 parser to be 2*sk_rcvbuf of the TCP socket.
 
-In general mode the message length limit is passed in as an argument
-to strp_process.
-
 Author
 ======