What's the format of tm->when in /proc/net/tcp?

Question

I need to know what tm->when means, but proc(5) doesn't mention anything helpful,

So, does it store the creation time of the socket? The number seems to be decreasing each time I view the file.

root@ubuntu-vm:~# cat /proc/net/tcp
  sl  local_address rem_address   st tx_queue rx_queue tr tm->when retrnsmt   uid  timeout inode                                                     
   0: 00000000:0CEA 00000000:0000 0A 00000000:00000000 00:00000000 00000000   104        0 17410 1 dddb6d00 100 0 0 10 -1                            
   1: 00000000:0016 00000000:0000 0A 00000000:00000000 00:00000000 00000000     0        0 7959 1 dddb4500 100 0 0 10 -1                             
   2: B238A8C0:0016 0138A8C0:9C96 01 00000000:00000000 02:00061444 00000000     0        0 8243 4 daa3c000 20 4 27 10 16                             
   3: B238A8C0:0CEA 0138A8C0:8753 01 00000000:00000000 02:0009C787 00000000   104        0 19467 2 daa3e300 20 4 18 10 -1

Answer 1

From Exploring the /proc/net/ Directory

The tr field indicates whether a timer is active for this socket. A value of zero indicates the timer is not active. The tm->when field indicates the time remaining (in jiffies) before timeout occurs.