halrmt: Allow IPv4 as fallback when IPv6 is disabled. - #4405
Open
BsAtHome wants to merge 1 commit into
Open
Conversation
grandixximo
reviewed
Aug 19, 2026
BsAtHome
force-pushed
the
fix_halrmt-ipv4
branch
from
August 19, 2026 16:03
62040e0 to
01968b7
Compare
grandixximo
reviewed
Aug 20, 2026
|
|
||
| static int getSocket4(struct sockaddr_in &addr, socklen_t &slen) | ||
| { | ||
| int sockfd = socket(AF_INET, SOCK_STREAM, 0); |
Contributor
There was a problem hiding this comment.
The refactor dropped SOCK_CLOEXEC | SOCK_NONBLOCK from both socket() calls here
and at line 2918. Master has them on the listen socket:
sockfd = socket(AF_INET6, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
and halrmt has no fcntl fallback anywhere, unlike emcrsh which calls
set_nonblock() after listen(). So the listener is now blocking and inheritable:
- accept4() after a spurious POLLIN blocks the poll loop indefinitely (accept(2)
BUGS: the connection can be aborted between poll and accept, leaving nothing
to take). That is the caveat from linuxcncrsh: IPv6-only listen socket fails to start when IPv6 is disabled #4401. - halrmt forks and execs at line 628, so every component it launches inherits
the listening fd and keeps port 5006 bound past halrmt's exit.
The first push had the flags on the IPv6 socket. Restoring them on both calls
should be all that is needed.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
The new halrmt server uses v4-mapped-on-v6 to have one socket accept both IPv6 and IPv4 connections. However, if IPv6 is disabled at the kernel command line (or not compiled in), then it would fail to create a listening socket. This PR adds an IPv4-only fallback in case IPv6 fails.