[Live-devel] UDP checksums validated in liveMedia ?

[Glen Gray]

Hey Guys,

Trying to get an mpeg decrypt module working with an MPEG2 TS from a 
Kasenna server. And I'm running into some problems.

Kernel has a callback function in udp.c, if the udp packet that was 
received is for a particular port then it'll pass over a **skbuff to a 
callback function. This function is in another module.

In that function, if the TS_SCRAMBLING_CONTROL flags are set and I clear 
them, then VLC never seems to get the data. However, if I simply comment 
out the clear code, everything seems to be fine.

Trying to figure out if I've a problem with my kernel patch (looking 
less and less likely, it's pretty trivial) or if it's a problem with 
liveMedia reading in the UDP data. I can't see any validation code in 
liveMedia, so I'm hoping you guys might be able to shed some light on this.

Initially I thought it could be the udp checksums being invalidated in 
the kernel after the manipulation of the mpeg data. So an addition I've 
made to the patch was to do the validation checks on the skbuf before 
handing it over to my external function. It also then sets the 
CHECKSUM_UNNECESSARY flag on the skb so that later on, the data should 
pass over the checksum checks. I'm not clear on if the checksums need to 
be recalculated.

Thanks in advance,

-- 
Glen Gray <glen at lincor.com>              Digital Depot, Thomas Street
Senior Software Engineer                            Dublin 8, Ireland
Lincor Solutions Ltd.                          Ph: +353 (0) 1 4893682