[linux-dvb] [Fwd: [patch 1/7] dvb-core: ULE fixes and RFC4326 additions]

Christian Prähauser cpraehaus at cosy.sbg.ac.at
Sat Apr 29 12:26:32 CEST 2006

Mauro Carvalho Chehab wrote:
> Is it ok to apply at our tree?
Well, it fixes some important issues (see below), especially regarding 
destination address (NPA) and ULE (optional) extension header 
processing, which is broken in the current kernel versions.

I would also opt for an attempt to rewrite the dvb networking (most of 
which is in dvb_net.c) part of dvb-core, because from my point of view, 
the ULE decaps code is overly complex.

This is how Andrew Morton formulated it:
> This driver would have to be one of the ugliest-looking things in the
> kernel. You must have a strong stomach.

README for dvb_net_ule_rfc4326.patch

Fixed bugs in the Unidirectional Lightweight Encapsulation (ULE) code. 
Also checked compliency with RFC 4326 (ULE).

Changes in dvb_net.c
* Fixed check of SNDU length.
The SNDU length was not checked correctly, thus leaving the possibility 
for a kernel panic if receiving malformed SNDUs.
Now, the SNDU length is considered invalid if it is less then 5. The 
reasoning for this is that an SNDU must always carry at least one byte 
of payload and the CRC32 (4 Bytes).

* Added check of return value from functions which handle mandatory 
extension headers (e.g. ule_test_sndu)

* Fixed handling of optional extension headers.
When processing optional extension headers, the length of the extension 
header was not calculated correctly.
Also the next header type field was assumed to be after the optional 
extension header. In fact, it is a part of it (always the last two bytes).
The length calc. and next header type field access for optional ext. 
headers have been fixed.

* Added handling of extension header padding (optional extension header 
with type 1)

* Fixed check of destination address in presence of extension headers.
The destination address was assumed to be after any extension headers. 
Thus, the extension headers were processed before comparing the 
destination address with the actual address of the receiver. After that, 
the total length of the ext. headers was removed from the buffer (skb) 
also including the destination address.
Now, the destination address (if present) is checked before processing 
any extension headers. The destination address is saved in a local 
buffer because it may be required for constructing the ethernet header.

* Fixed/Improved filtering on destination address (if present in ULE SNDU)
(1) Now, everything is passed up the stack if in promiscious mode.
(2) The address of the receiver device and the broadcast address 
(FF:FF:FF:FF:FF:FF) are always accepted.
(3) If in multicast mode, all addresses in the multicast address list 
are accepted (in addition to 2).
(4) If in all-multicast mode, all multicast addresses are accepted (in 
addition to 2).

* Reduced timeout value for TS cells to 10 ms.

* Fixed arguments for setting TS feed properties.
The documentation for DVB-API v3 and what is actually present in the 
Linux kernel seem to be out of sync.
The set() function for TS feeds differs in the DVB API version 3 
document and the Linux kernel version:
int set(dmx ts feed t* feed, u16 pid, size_t callback length, size_t 
circular buffer size, int descramble, struct timespec timeout);
Actually implemented in the 2.6.15 Kernel:
int dmx_ts_feed_set(struct dmx_ts_feed *ts_feed, u16 pid, int ts_type, 
enum dmx_ts_pes pes_type, size_t circular_buffer_size, struct timespec 

Patch Author
Christian Praehauser
Paris Lodron University of Salzburg

Signed-off-by: Christian Praehauser <cpraehaus at cosy.sbg.ac.at>

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