The original source for this version of the rumor came from this photo that was posted on the Al Manara Facebook page, showing weapons that Libyan rebels captured:
The weapon has a six pointed star imprinted on it, hence, it was assumed to be from Israel.
Al Jazeera also showed video of these weapons and highlighted the six-pointed star as proof that they came from Israel (go to 0:22)
Iran's Press TV jumped on the bandwagon:
The opposition forces in the Libyan city of Misratah displayed weapons that they have seized from the forces supporting Libyan leader Muammar Gaddafi, Al Jazeera reported Thursday.
They said that some of the confiscated rockets and bombs had signs imprinted on them, clearly indicating that they are manufactured in Israel.
However, in a fascinating Twitter thread, the entire basis for this rumor was demolished in minutes.
The upshot is that this is a universal symbol for an illuminating flare (star) that uses a parachute (umbrella symbol). From a NATO manual:
The six-pointed star has been used for identifying illumination rounds since at least World War I.
The rumor is completely and provably false. And not one of those who spread the rumor will ever recant, because truth is not their objective.
(What has not been proven false is whether Dahlan had been involved in weapons smuggling for Libya in general. I have no information either way on that.)