Coghlans's Mosquito Coils - 10 Pack is an effective anti-mosquito product that gives off d-cis trans allethrin when lit, which kills and repels mosquitoes.
Coghlans says:
10-pack of coils that kill and repel mosquitoes. Each coil will burn upto 8 hours.
Active ingredient: 0.23% d-cis trans allethrin.
We know of at least one backpacker who swears by these coils from Coghlans. Lighting one in the porch each evening and morning does the trick (however that's not a recommendation, we don't recommend lighting anything in a tent porch).