1Demonstrations of tcpsynbl, the Linux BCC/eBPF version. 2 3 4This tool shows the TCP SYN backlog size during SYN arrival as a histogram. 5This lets you see how close your applications are to hitting the backlog limit 6and dropping SYNs (causing performance issues with SYN retransmits). For 7example: 8 9# ./tcpsynbl.py 10Tracing SYN backlog size. Ctrl-C to end. 11^C 12 13backlog_max = 500L 14 backlog : count distribution 15 0 -> 1 : 961 |****************************************| 16 2 -> 3 : 1 | | 17 18This output shows that for the backlog limit of 500, there were 961 SYN 19arrival where the backlog was zero or one, and one accept where the backlog was 20two or three. This indicates that we are nowhere near this limit. 21 22USAGE: 23 24# ./tcpsynbl -h 25usage: tcpsynbl.py [-h] [-4 | -6] 26 27Show TCP SYN backlog. 28 29optional arguments: 30 -h, --help show this help message and exit 31 -4, --ipv4 trace IPv4 family only 32 -6, --ipv6 trace IPv6 family only 33 34examples: 35 ./tcpsynbl # trace syn backlog 36 ./tcpsynbl -4 # trace IPv4 family only 37 ./tcpsynbl -6 # trace IPv6 family only