Linux kernel variable that says to drop packets coming from an interface to which there is no route?

Question

linux

Is there such a thing?
The situation is as follows, I raised the ip gre tunnel, everything works, everything pings, if I raise the route to google.com through the tunnel (with a simple ip route add), then the curl -i tnl0 google.com command works, if I don’t raise it, it doesn’t work, although I see it in tcpdump that packages go to Google and come perfectly.
Approximately like this

09:21:12.558492 IP 192.168.2.1.41340 &gt; 74.125.127.103.80: Flags [S], seq 3377743775, win 5760, options [mss 1440,sackOK,TS val 4089648 ecr 0,nop,wscale 6], length 0<br/>
09:21:12.652384 IP 74.125.127.103.80 &gt; 192.168.2.1.41340: Flags [S.], seq 3838110306, ack 3377743776, win 5672, options [mss 1430,sackOK,TS val 3885334725 ecr 4089348,nop,wscale 6], length 0<br/>
09:21:14.255327 IP 74.125.127.103.80 &gt; 192.168.2.1.41340: Flags [S.], seq 3838110306, ack 3377743776, win 5672, options [mss 1430,sackOK,TS val 3885336328 ecr 4089348,nop,wscale 6], length 0<br/>

Answer 1

net.ipv4.conf.default.rp_filter = 1
Is this?