[PATCH net-next] net: sctp: sctp_verify_init: clean up mandatory checks and add comment

[PATCH net-next] net: sctp: sctp_verify_init: clean up mandatory checks and add comment

[Daniel Borkmann]

Add a comment related to RFC4960 explaning why we do not check for initial
TSN, and while at it, remove yoda notation checks and clean up code from
checks of mandatory conditions. That's probably just really minor, but makes
reviewing easier.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
---
 net/sctp/sm_make_chunk.c | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 01e9783..c6ca3c9 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -2240,25 +2240,23 @@ int sctp_verify_init(struct net *net, const struct sctp_association *asoc,
 		     struct sctp_chunk **errp)
 {
 	union sctp_params param;
-	int has_cookie = 0;
+	bool has_cookie = false;
 	int result;
 
-	/* Verify stream values are non-zero. */
-	if ((0 == peer_init->init_hdr.num_outbound_streams) ||
-	    (0 == peer_init->init_hdr.num_inbound_streams) ||
-	    (0 == peer_init->init_hdr.init_tag) ||
-	    (SCTP_DEFAULT_MINWINDOW > ntohl(peer_init->init_hdr.a_rwnd))) {
-
+	/* Check for missing mandatory parameters. Note: Initial TSN is also
+	 * mandatory, but not checked here since range is possible from 0 to
+	 * 2**32-1 (4294967295), RFC4960 3.3.3.
+	 */
+	if (peer_init->init_hdr.num_outbound_streams == 0 ||
+	    peer_init->init_hdr.num_inbound_streams == 0 ||
+	    peer_init->init_hdr.init_tag == 0 ||
+	    ntohl(peer_init->init_hdr.a_rwnd) < SCTP_DEFAULT_MINWINDOW)
 		return sctp_process_inv_mandatory(asoc, chunk, errp);
-	}
 
-	/* Check for missing mandatory parameters.  */
 	sctp_walk_params(param, peer_init, init_hdr.params) {
-
-		if (SCTP_PARAM_STATE_COOKIE == param.p->type)
-			has_cookie = 1;
-
-	} /* for (loop through all parameters) */
+		if (param.p->type == SCTP_PARAM_STATE_COOKIE)
+			has_cookie = true;
+	}
 
 	/* There is a possibility that a parameter length was bad and
 	 * in that case we would have stoped walking the parameters.
-- 
1.7.11.7

Re: [PATCH net-next] net: sctp: sctp_verify_init: clean up mandatory checks and add comment

[Neil Horman]

On Tue, Aug 27, 2013 at 03:23:50PM +0200, Daniel Borkmann wrote:
> Add a comment related to RFC4960 explaning why we do not check for initial
> TSN, and while at it, remove yoda notation checks and clean up code from
> checks of mandatory conditions. That's probably just really minor, but makes
> reviewing easier.
> 
> Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
> ---
>  net/sctp/sm_make_chunk.c | 26 ++++++++++++--------------
>  1 file changed, 12 insertions(+), 14 deletions(-)
> 
> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
> index 01e9783..c6ca3c9 100644
> --- a/net/sctp/sm_make_chunk.c
> +++ b/net/sctp/sm_make_chunk.c
> @@ -2240,25 +2240,23 @@ int sctp_verify_init(struct net *net, const struct sctp_association *asoc,
>  		     struct sctp_chunk **errp)
>  {
>  	union sctp_params param;
> -	int has_cookie = 0;
> +	bool has_cookie = false;
>  	int result;
>  
> -	/* Verify stream values are non-zero. */
> -	if ((0 == peer_init->init_hdr.num_outbound_streams) ||
> -	    (0 == peer_init->init_hdr.num_inbound_streams) ||
> -	    (0 == peer_init->init_hdr.init_tag) ||
> -	    (SCTP_DEFAULT_MINWINDOW > ntohl(peer_init->init_hdr.a_rwnd))) {
> -
> +	/* Check for missing mandatory parameters. Note: Initial TSN is also
> +	 * mandatory, but not checked here since range is possible from 0 to
> +	 * 2**32-1 (4294967295), RFC4960 3.3.3.
> +	 */
nit: If we're making this easier to review, I think the above would be easier to
read if it said:
Note: Initial TSN is also mandatory, but is not checked here since the valid
range is 0..2**(32-1)

> +	if (peer_init->init_hdr.num_outbound_streams == 0 ||
> +	    peer_init->init_hdr.num_inbound_streams == 0 ||
> +	    peer_init->init_hdr.init_tag == 0 ||
> +	    ntohl(peer_init->init_hdr.a_rwnd) < SCTP_DEFAULT_MINWINDOW)
>  		return sctp_process_inv_mandatory(asoc, chunk, errp);
> -	}
>  
> -	/* Check for missing mandatory parameters.  */
>  	sctp_walk_params(param, peer_init, init_hdr.params) {
> -
> -		if (SCTP_PARAM_STATE_COOKIE == param.p->type)
> -			has_cookie = 1;
> -
> -	} /* for (loop through all parameters) */
> +		if (param.p->type == SCTP_PARAM_STATE_COOKIE)
> +			has_cookie = true;
> +	}
>  
>  	/* There is a possibility that a parameter length was bad and
>  	 * in that case we would have stoped walking the parameters.
> -- 
> 1.7.11.7
> 
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Re: [PATCH net-next] net: sctp: sctp_verify_init: clean up mandatory checks and add comment

[Daniel Borkmann]

On 08/27/2013 03:43 PM, Neil Horman wrote:

> nit: If we're making this easier to review, I think the above would be easier to
> read if it said:
> Note: Initial TSN is also mandatory, but is not checked here since the valid
> range is 0..2**(32-1)

Ok, will send a v2 in a moment.