Eric Dumazet says:
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inet: prevent skb changes in udp{4|6}_lib_lookup_skb()
This came while reviewing Alexander Lobakin patch against UDP GRO:
We want to make sure skb wont be changed by these helpers
while it is owned by GRO stack.
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Link: https://lore.kernel.org/r/20201109231349.20946-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>