have multiple macOS machines with 600-1000+ day uptimes, which do TCP connections every minute or so...

justinfrankel • yesterday at 9:19 PM • 2 replies • view on HN

have multiple macOS machines with 600-1000+ day uptimes, which do TCP connections every minute or so at a minimum, they are still expiring their TIME_WAIT connections as normal.

these kernel versions:

Darwin Kernel Version 20.6.0: Thu Jul 6 22:12:47 PDT 2023; root:xnu-7195.141.49.702.12~1/RELEASE_ARM64_T8101 arm64

Darwin Kernel Version 17.7.0: Wed Apr 24 21:17:24 PDT 2019; root:xnu-4570.71.45~1/RELEASE_X86_64 x86_64

so... wonder what that's about?

Replies

justinfrankel • yesterday at 9:30 PM

ah reading their analysis, there are errors that explain this. Particularly this:

  tcp_now   = 4,294,960,000  (frozen at pre-overflow value)
  timer     = 4,294,960,000 + 30,000 = 4,294,990,000
              (exceeds uint32 max → wraps to a small number)

timer wraps to a small number, they say

  TSTMP_GEQ(4294960000, 4294990000)

they forgot to wrap it there, it should be TSTMP_GEQ(4294960000, small_number)

  = (int)(4294960000 - 4294990000)
  = (int)(-30000)
  = -30000 >= 0 ?  → false!

wrong!

There may be a short time period where this bug occurs, and if you get enough TCP connections to TIME_WAIT in that period, they could stick around, maybe. But I think the original post is completely overreacting and was probably written by a LLM, lol.

alt Hacker News

Replies