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HDHomeRun TTL Mangling with IPTables on OpenWRT
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| If you have a HDHomeRun tuner behind an OpenWRT device such as a cheap Gl-inet router (and within the 3 hop limit), you can very easily break the TTL packet setting that is now set on these devices with a simple shell command. | |
| Based upon this work https://stuff.purdon.ca/?page_id=472 | |
| I figured out I could just add | |
| iptables -t mangle -A FORWARD -s <hdhrip> -j TTL --ttl-set 64 | |
| iptables -t nat -A POSTROUTING -j MASQUERADE | |
| to the existing rules and it would do what was required. Just add this command, replacing the <hdhrip> with the IP address of the HDHomerun box(s), into your startup scripts, and off you go - HDHomerun DVB TV via the internet once again. |
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Also this seems to be useful
iptables -t mangle -A FORWARD -j TTL --ttl-inc 5
https://unix.stackexchange.com/questions/605497/overriding-ip-packet-ttls
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Testing what the TTL is on an interface in OpenWRT
iptables -t mangle -I POSTROUTING -o wwan0 -j TTL --ttl-set 127
tcpdump: listening on wwan0, link-type RAW (Raw IP), capture size 262144 bytes
21:17:38.649477 IP (tos 0x0, ttl 127, id 53293, offset 0, flags [DF], proto ICMP (1), length 84)
10.174.174.174 > one.one.one.one: ICMP echo request, id 28781, seq 0, length 64
21:17:38.791432 IP (tos 0x0, ttl 54, id 60777, offset 0, flags [none], proto ICMP (1), length 84)
one.one.one.one > 10.174.174.174: ICMP echo reply, id 28781, seq 0, length 64