From: Florian Obser <florian@openbsd.org>
Subject: Remove net.inet6.ip6.auto_flowlabel knob.
To: tech <tech@openbsd.org>
Date: Mon, 15 Sep 2025 16:45:02 +0200

There is no reason not to do flowlabels.

OK?

diff --git lib/libc/sys/sysctl.2 lib/libc/sys/sysctl.2
index b4a34f2748c..412ead4fa01 100644
--- lib/libc/sys/sysctl.2
+++ lib/libc/sys/sysctl.2
@@ -1842,7 +1842,6 @@ The currently defined protocols and names are:
 .It icmp6 Ta nd6_mmaxtries Ta integer Ta yes
 .It icmp6 Ta nd6_umaxtries Ta integer Ta yes
 .It icmp6 Ta redirtimeout Ta integer Ta yes
-.It ip6 Ta auto_flowlabel Ta integer Ta yes
 .It ip6 Ta dad_count Ta integer Ta yes
 .It ip6 Ta dad_pending Ta integer Ta yes
 .It ip6 Ta defmcasthlim Ta integer Ta yes
@@ -1919,11 +1918,6 @@ constant in IPv6 neighbor discovery specification
 The variable specifies the lifetime of routing entries generated by
 incoming ICMPv6 redirects.
 .Pp
-.It Li ip6.auto_flowlabel Pq Va net.inet6.ip6.auto_flowlabel
-On connected transport protocol packets,
-fill the IPv6 flowlabel field to help intermediate routers identify
-packet flows.
-.Pp
 .It Li ip6.dad_count Pq Va net.inet6.ip6.dad_count
 This variable configures the number of IPv6 DAD
 .Pq duplicated address detection
diff --git sys/netinet6/in6.h sys/netinet6/in6.h
index a6826e8756e..21d387e8167 100644
--- sys/netinet6/in6.h
+++ sys/netinet6/in6.h
@@ -619,7 +619,7 @@ ifatoia6(struct ifaddr *ifa)
 	{ 0, 0 }, \
 	{ "hdrnestlimit", CTLTYPE_INT }, \
 	{ "dad_count", CTLTYPE_INT }, \
-	{ "auto_flowlabel", CTLTYPE_INT }, \
+	{ 0, 0 }, \
 	{ "defmcasthlim", CTLTYPE_INT }, \
 	{ 0, 0 }, \
 	{ 0, 0 }, \
diff --git sys/netinet6/in6_pcb.c sys/netinet6/in6_pcb.c
index a23203bf274..5577eba12e6 100644
--- sys/netinet6/in6_pcb.c
+++ sys/netinet6/in6_pcb.c
@@ -334,10 +334,8 @@ in6_pcbconnect(struct inpcb *inp, struct mbuf *nam)
 	mtx_leave(&table->inpt_mtx);
 
 	inp->inp_flowinfo &= ~IPV6_FLOWLABEL_MASK;
-	if (atomic_load_int(&ip6_auto_flowlabel)) {
-		inp->inp_flowinfo |=
-		    (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK);
-	}
+	inp->inp_flowinfo |=
+	    (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK);
 #if NSTOEPLITZ > 0
 	inp->inp_flowid = stoeplitz_ip6port(&inp->inp_faddr6,
 	    &inp->inp_laddr6, inp->inp_fport, inp->inp_lport);
@@ -730,10 +728,8 @@ in6_pcbset_addr(struct inpcb *inp, const struct sockaddr_in6 *fsin6,
 	mtx_leave(&table->inpt_mtx);
 
 	inp->inp_flowinfo &= ~IPV6_FLOWLABEL_MASK;
-	if (atomic_load_int(&ip6_auto_flowlabel)) {
-		inp->inp_flowinfo |=
-		    (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK);
-	}
+	inp->inp_flowinfo |=
+	    (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK);
 #if NSTOEPLITZ > 0
 	inp->inp_flowid = stoeplitz_ip6port(&inp->inp_faddr6,
 	    &inp->inp_laddr6, inp->inp_fport, inp->inp_lport);
diff --git sys/netinet6/in6_proto.c sys/netinet6/in6_proto.c
index 1f13bba4191..1e74ef6b401 100644
--- sys/netinet6/in6_proto.c
+++ sys/netinet6/in6_proto.c
@@ -360,7 +360,6 @@ int	ip6_maxfrags = 200;	/* [a] */
 int	ip6_hdrnestlimit = 10;	/* [a] appropriate? */
 int	ip6_dad_count = 1;	/* [a] DupAddrDetectionTransmits */
 int	ip6_dad_pending;	/* number of currently running DADs */
-int	ip6_auto_flowlabel = 1;	/* [a] */
 int	ip6_mcast_pmtu = 0;	/* [a] enable pMTU discovery for multicast? */
 int	ip6_neighborgcthresh = 2048; /* [a] Threshold # of NDP entries for GC */
 int	ip6_maxdynroutes = 4096; /* [a] Max # of routes created via redirect */
diff --git sys/netinet6/ip6_input.c sys/netinet6/ip6_input.c
index 37680d7fe52..4de688e4690 100644
--- sys/netinet6/ip6_input.c
+++ sys/netinet6/ip6_input.c
@@ -1449,7 +1449,6 @@ const struct sysctl_bounded_args ipv6ctl_vars[] = {
 	{ IPV6CTL_MAXFRAGPACKETS, &ip6_maxfragpackets, 0, 1000 },
 	{ IPV6CTL_HDRNESTLIMIT, &ip6_hdrnestlimit, 0, 100 },
 	{ IPV6CTL_DAD_COUNT, &ip6_dad_count, 0, 10 },
-	{ IPV6CTL_AUTO_FLOWLABEL, &ip6_auto_flowlabel, 0, 1 },
 	{ IPV6CTL_DEFMCASTHLIM, &ip6_defmcasthlim, 0, 255 },
 	{ IPV6CTL_MAXFRAGS, &ip6_maxfrags, 0, 1000 },
 	{ IPV6CTL_MFORWARDING, &ip6_mforwarding, 0, 1 },
diff --git sys/netinet6/ip6_var.h sys/netinet6/ip6_var.h
index 37f733dfd7d..075be22d3c5 100644
--- sys/netinet6/ip6_var.h
+++ sys/netinet6/ip6_var.h
@@ -293,8 +293,6 @@ extern int	ip6_hdrnestlimit; /* upper limit of # of extension headers */
 extern int	ip6_dad_count;		/* DupAddrDetectionTransmits */
 extern int	ip6_dad_pending;	/* number of currently running DADs */
 
-extern int ip6_auto_flowlabel;
-
 extern const struct pr_usrreqs rip6_usrreqs;
 
 struct inpcb;

-- 
In my defence, I have been left unsupervised.