tcpdump --diagnose
SYN Cookie Checker
Companion to SYN flood detection lies to you on a SYN-cookie kernel. Paste output below, nothing leaves your browser.
Commands to gather this
sysctl net.ipv4.tcp_syncookies
ss -tn state syn-recv | wc -l
cat /proc/sys/net/ipv4/tcp_max_syn_backlog