tcp dport fetching with ftrace on linux 3.13 x86_64

gistfile1.txt

Using my perf-tools just to wrap ftrace:

# ./perf-tools/bin/kprobe 'p:tcp_v4_connect skc_dport=+2(%si):u16' 
Tracing kprobe tcp_v4_connect. Ctrl-C to end.
          telnet-9723  [001] d... 62326244.175951: tcp_v4_connect: (tcp_v4_connect+0x0/0x480) skc_dport=1600
          telnet-9725  [001] d... 62326246.502760: tcp_v4_connect: (tcp_v4_connect+0x0/0x480) skc_dport=1700
          telnet-9726  [001] d... 62326247.861937: tcp_v4_connect: (tcp_v4_connect+0x0/0x480) skc_dport=100
          telnet-9727  [001] d... 62326249.220740: tcp_v4_connect: (tcp_v4_connect+0x0/0x480) skc_dport=e803
          
Now a crappy ntohs() to process the dport string:

# ./perf-tools/bin/kprobe 'p:tcp_v4_connect skc_dport=+2(%si):u16' | perl -ne 'chomp; if (/.*=(.*)/) { $n = "000" . $1; print "port: " . hex(substr($n, -2, 2) . substr($n, -4, 2)) . "\n"}'
port: 22
port: 23
port: 1
port: 1000

And that matches my known workload.