from Hacker News

Ask HN: Why is iOS 17 setting TCP reserved bit?

by GGO on 9/4/23, 10:44 PM with 12 comments

I started using iOS 17 beta and I am noticing that websites take long to load. I looked at my firewall logs and it looks like safari on new iOS is setting reserved bit in which firewall's IPS engine is blocking right away: Invalid TCP reserved bit. This is not happening on iOS 16.

Is there some hidden TCP change with iOS 17 that is now secretly using those TCP reserved bits?

  • by mikequinlan on 9/4/23, 10:55 PM

    Are you using iCloud Private Relay? Is it possible that their third-party content provider is setting that?

  • by wmf on 9/5/23, 1:16 AM

  • by Ocha on 9/4/23, 11:14 PM

    TIL there is TCP reserved bits

  • by Ocha on 9/4/23, 11:13 PM

    Would be nice to see a TDP dump of before and after upgrade. Is there a way to get it on iOS?

  • by dtaht on 9/4/23, 11:13 PM

    Which TCP reserved bit? ECN? The reserved fields in the ack?