From 0ba8374bb8a7032ca13ba98d10e8d7c3378ca9c6 Mon Sep 17 00:00:00 2001
From: Susant Sahani <ssahani@gmail.com>
Date: Fri, 8 Sep 2023 14:30:38 +0530
Subject: [PATCH] ndisc: Also set link hoplimit

The per route hop limit does not place the hop limit in the IPv6 header.
https://github.com/systemd/systemd/issues/28437#issuecomment-1711055181
---
 src/network/networkd-ndisc.c  | 7 ++++++-
 src/network/networkd-sysctl.c | 2 +-
 src/network/networkd-sysctl.h | 1 +
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/network/networkd-ndisc.c b/src/network/networkd-ndisc.c
index 08af9c73b99..f4f662cf965 100644
--- a/src/network/networkd-ndisc.c
+++ b/src/network/networkd-ndisc.c
@@ -199,7 +199,12 @@ static int ndisc_request_route(Route *in, Link *link, sd_ndisc_router *rt) {
                 r = sd_ndisc_router_get_hop_limit(rt, &hop_limit);
                 if (r < 0 && r != -ENODATA)
                         return log_link_warning_errno(link, r, "Failed to get default router hop limit from RA: %m");
-        }
+
+                link->network->ipv6_hop_limit = hop_limit;
+                r = link_set_ipv6_hop_limit(link);
+                if (r < 0)
+                        log_link_warning_errno(link, r, "Cannot set IPv6 hop limit for interface, ignoring: %m");
+       }
 
         route->source = NETWORK_CONFIG_SOURCE_NDISC;
         route->provider.in6 = router;
diff --git a/src/network/networkd-sysctl.c b/src/network/networkd-sysctl.c
index 0b8169a0176..1a5dffe6f59 100644
--- a/src/network/networkd-sysctl.c
+++ b/src/network/networkd-sysctl.c
@@ -165,7 +165,7 @@ static int link_set_ipv6_dad_transmits(Link *link) {
         return sysctl_write_ip_property_int(AF_INET6, link->ifname, "dad_transmits", link->network->ipv6_dad_transmits);
 }
 
-static int link_set_ipv6_hop_limit(Link *link) {
+int link_set_ipv6_hop_limit(Link *link) {
         assert(link);
 
         /* Make this a NOP if IPv6 is not available */
diff --git a/src/network/networkd-sysctl.h b/src/network/networkd-sysctl.h
index 064438462c0..99243f7a25d 100644
--- a/src/network/networkd-sysctl.h
+++ b/src/network/networkd-sysctl.h
@@ -28,6 +28,7 @@ typedef enum IPReversePathFilter {
 
 int link_set_sysctl(Link *link);
 int link_set_ipv6_mtu(Link *link);
+int link_set_ipv6_hop_limit(Link *link);
 
 const char* ipv6_privacy_extensions_to_string(IPv6PrivacyExtensions i) _const_;
 IPv6PrivacyExtensions ipv6_privacy_extensions_from_string(const char *s) _pure_;