This appears to be an oleander hawk-moth caterpillar ( _Daphnis nerii_ ) shortly before pupating. Otherwise the caterpillar would be bright green in colour:
> Newly hatched oleander hawk-moth larvae are three to four millimeters in length, bright yellow, and have a black, elongated "horn" on the rear of the body. … As they get older, the larvae become green to brown with a large blue-and-white eyespot near the head and a yellow "horn" on the rear. […] Just before it pupates, the oleander hawk-moth larva becomes browner in colour.