From: "Theo de Raadt" <deraadt@openbsd.org>
Subject: Re: chromium: disable IP_TOS for UDP
To: robert@openbsd.org, ports@openbsd.org
Date: Tue, 08 Sep 2026 17:55:31 -0600

Kirill A. Korinsky <kirill@korins.ky> wrote:

> Seems that new chromium plays with TOS at UDP for HTTP/3 and our pledge
> prevents it, and kills the process. It dumps ~100Mb core and after that it
> fallback to HTTP/1.1.

We are encountering this too many places, so I'd like everyone to consider
this 2-step approach, becuase Linux dual-stack has utterly poisoned the
ecosystem and noone looks at setsockopt return values accurately.

1. netinet6 accepts IPPROTO_IP/IP_TOS and converts it to IPPROTO_IPV6/IPV6_TCLASS

2. For programs which are pledged, allow that through

Index: netinet6/ip6_output.c
===================================================================
RCS file: /cvs/src/sys/netinet6/ip6_output.c,v
diff -u -p -u -r1.308 ip6_output.c
--- netinet6/ip6_output.c	5 Aug 2026 09:43:19 -0000	1.308
+++ netinet6/ip6_output.c	8 Sep 2026 23:53:46 -0000
@@ -1032,6 +1032,12 @@ ip6_ctloutput(int op, struct socket *so,
 	privileged = (inp->inp_socket->so_state & SS_PRIV);
 	uproto = (int)so->so_proto->pr_protocol;
 
+	/* Linux poisoned the ecosystem */
+	if (level == IPPROTO_IP && optname == IP_TOS) {
+		level = IPPROTO_IPV6;
+		optname = IPV6_TCLASS;
+	}
+
 	if (level != IPPROTO_IPV6)
 		return (EINVAL);
 

Index: kern/kern_pledge.c
===================================================================
RCS file: /cvs/src/sys/kern/kern_pledge.c,v
diff -u -p -u -r1.365 kern_pledge.c
--- kern/kern_pledge.c	4 Sep 2026 02:38:28 -0000	1.365
+++ kern/kern_pledge.c	8 Sep 2026 23:37:52 -0000
@@ -1451,9 +1464,17 @@ pledge_sockopt(struct proc *p, int set, 
 		}
 		break;
 	case AF_INET6:
-		if (level == IPPROTO_IPV6) {
+		switch (level) {
+		case IPPROTO_IPV6:
 			switch (optname) {
 			case IPV6_TCLASS:
+				return (0);
+			}
+			break;
+		/* Because Linux makes the universe stink */
+		case IPPROTO_IP:
+			switch (optname) {
+			case IP_TOS:
 				return (0);
 			}
 		}