SYN stall check

Runs from a box at Frank's house. For 30 seconds it opens TCP connections back to back to xyTel servers that sit behind a stateful firewall (conntrack), plus two controls with no conntrack, and pings a few well-known addresses. Everything alternates between the PUD GPON link and Starlink for comparison. A connection that takes more than 0.9 s means its first SYN was dropped.