There are the Dhammapada verses 129, 130, 131, and 405, that praise noncruelty to animals, and prohibit cruelty to animals based on one's greed (for their meat). This topic next leads to the wornout issue of vegetarianism, to me it seems very clear that Dhammapada forbids all greed based consumption of and demand for meat. If you can eat meat without having a greed for it, it might be OK in some circumstances, otherwise not. At the same time Buddha knew that you can't enforce vegetarianism. You can't make a law of it, it wont work. This dilemma and this view is expressed in the Lankavatara sutra, therefore I see no reason to doubt its authenticity as an original teaching of Buddha Shakyamuni. It is very difficult because the habitual tendencies for meat eating are very strong, and they cause corresponding interpretations of Dharma to appear. I see the Lankavatara chapter as a more original text than all the corresponding Theravada texts that blatantly allow meat eating.
Then you have other Mahayana texts like Parinirvana sutra and the Avalokitesvara fasting practice texts that prohibit meat eating, and the Brahma net sutra, as has been said already. Buddha didn't a make a law of vegetarianism, he must have been aware of the consequences that would follow from such a policy, he says it in the Lankavatara after a lengthy praise of vegetarianism.