> On 6 Jan 2023, at 14:18, Sjoerd Mullender <sjoerd@xxxxxxx> wrote: > > I have a program that is supposed to listen to the same port on both IPv4 and IPv6 sockets. In the past, what it did, was basically: create new socket for IPv6, set option IPV6_V6ONLY to off, bind, listen; then create a new socket for IPv4, and also bind and listen. The first bind is either to a specific port, or to port 0 to let the system assign a port. The second bind uses the port that the first one used (i.e. what the system assigned). Are you sure that this is behaviour you can depend on? Is it documented? It seems that there is a possibility that the 2nd bind with port 0 can race against other processes. Why should you get the same port bound? If I was writing this code I would take the port allocated on the 1st bind and use it explicitly in the 2nd bind. Would that work and be deterministic? I recall working on code that needed two ports N and N+1. The algorithm looped until the N and N+1 condition was met. Barry > > With the latest kernel, this still works if listening to localhost ([::1]/127.0.0.1) only, but not when listening to [::]/0.0.0.0. In that case, the second bind gets a different port number assigned to it. Moreover, the second bind system call returns 1, which it is not supposed to do according to the manual. Bind is supposed to return 0 on success and -1 on error. > > What is going on? Is this a kernel bug, or is this the future? > > Kernel is 6.0.16-300.fc37.x86_64, i.e. the latest Fedora 37 kernel. > > -- > Sjoerd Mullender > _______________________________________________ > users mailing list -- users@xxxxxxxxxxxxxxxxxxxxxxx > To unsubscribe send an email to users-leave@xxxxxxxxxxxxxxxxxxxxxxx > Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ > List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines > List Archives: https://lists.fedoraproject.org/archives/list/users@xxxxxxxxxxxxxxxxxxxxxxx > Do not reply to spam, report it: https://pagure.io/fedora-infrastructure/new_issue _______________________________________________ users mailing list -- users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to users-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/users@xxxxxxxxxxxxxxxxxxxxxxx Do not reply to spam, report it: https://pagure.io/fedora-infrastructure/new_issue
