linux dnsmasq: how do I increase the ttl?

I don't think you can, not easily. The TTL is set by Google's nameservers and they like it low for loadbalancing purposes.

It's possible that increasing the cache size could help, but for super-short TTLs like Google's it probably won't.

Unofficially, there are a couple of patches to provide a TTL-override functionality. I found these on the dnsmasq-discuss mailing list, so if you feel like rolling your own, try them out (you might check the mailing list archives for patches against more recent versions):

• patch for v2.22, adds "min-ttl" option (this is what you describe, though it may not apply cleanly to current versions)
• patch for v2.41, adds "pos-ttl" option (can't tell if this will do the same thing or not)