[pve-devel] [PATCH lxc] patch dhclient-script to set RFC3442 classless routes

[Filip Schauer <f.schauer@proxmox.com>]

Embed the rfc3442-classless-routes hook from isc-dhcp-client into the
LXC dhclient-script. This is needed by application containers with
host-managed DHCP network interfaces, that receive routes via DHCP
option 121 (RFC3442).

Previously these classless routes were ignored.
This was originally reported in the Proxmox forum [0].

[0] https://forum.proxmox.com/threads/no-default-gateway-on-oci-container-with-dhcp.176696/

Signed-off-by: Filip Schauer <f.schauer@proxmox.com>
---
 ...3-PVE-apply-rfc3442-classless-routes.patch | 106 ++++++++++++++++++
 debian/patches/series                         |   1 +
 2 files changed, 107 insertions(+)
 create mode 100644 debian/patches/pve/0003-PVE-apply-rfc3442-classless-routes.patch

diff --git a/debian/patches/pve/0003-PVE-apply-rfc3442-classless-routes.patch b/debian/patches/pve/0003-PVE-apply-rfc3442-classless-routes.patch
new file mode 100644
index 0000000..26ab883
--- /dev/null
+++ b/debian/patches/pve/0003-PVE-apply-rfc3442-classless-routes.patch
@@ -0,0 +1,106 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Filip Schauer <f.schauer@proxmox.com>
+Date: Wed, 3 Dec 2025 15:03:50 +0100
+Subject: [PATCH] dhclient-script: set RFC3442 classless routes
+
+Due to the removal of hooks in the LXC fork of dhclient-script, the
+rfc3442-classless-routes hook did not run. As a result, classless static
+routes received from the DHCP server were ignored.
+
+This commit restores support for RFC3442 classless routes by embedding
+the code from /etc/dhcp/dhclient-exit-hooks.d/rfc3442-classless-routes
+from the isc-dhcp-client package.
+
+Signed-off-by: Filip Schauer <f.schauer@proxmox.com>
+---
+ hooks/dhclient-script | 67 +++++++++++++++++++++++++++++++++++++++++++
+ 1 file changed, 67 insertions(+)
+
+diff --git a/hooks/dhclient-script b/hooks/dhclient-script
+index 9c9b40e69..c87792707 100755
+--- a/hooks/dhclient-script
++++ b/hooks/dhclient-script
+@@ -133,6 +133,71 @@ set_hostname() {
+     fi
+ }
+ 
++# Code adapted from isc-dhcp-client rfc3442-classless-routes hook
++set_rfc3442_classless_routes() {
++    set -- $new_rfc3442_classless_static_routes
++
++    while [ $# -gt 0 ]; do
++        net_length=$1
++        via_arg=''
++
++        case $net_length in
++            32|31|30|29|28|27|26|25)
++                if [ $# -lt 9 ]; then
++                    return 1
++                fi
++                net_address="${2}.${3}.${4}.${5}"
++                gateway="${6}.${7}.${8}.${9}"
++                shift 9
++                ;;
++            24|23|22|21|20|19|18|17)
++                if [ $# -lt 8 ]; then
++                    return 1
++                fi
++                net_address="${2}.${3}.${4}.0"
++                gateway="${5}.${6}.${7}.${8}"
++                shift 8
++                ;;
++            16|15|14|13|12|11|10|9)
++                if [ $# -lt 7 ]; then
++                    return 1
++                fi
++                net_address="${2}.${3}.0.0"
++                gateway="${4}.${5}.${6}.${7}"
++                shift 7
++                ;;
++            8|7|6|5|4|3|2|1)
++                if [ $# -lt 6 ]; then
++                    return 1
++                fi
++                net_address="${2}.0.0.0"
++                gateway="${3}.${4}.${5}.${6}"
++                shift 6
++                ;;
++            0)      # default route
++                if [ $# -lt 5 ]; then
++                    return 1
++                fi
++                net_address="0.0.0.0"
++                gateway="${2}.${3}.${4}.${5}"
++                shift 5
++                ;;
++            *)      # error
++                return 1
++                ;;
++        esac
++
++        # take care of link-local routes
++        if [ "${gateway}" != '0.0.0.0' ]; then
++            via_arg="via ${gateway}"
++        fi
++
++        # set route (ip detects host routes automatically)
++        ${ip} -4 route add "${net_address}/${net_length}" \
++            ${via_arg} dev "${interface}" >/dev/null 2>&1
++    done
++}
++
+ # Execute the operation
+ case "$reason" in
+ 
+@@ -207,6 +272,8 @@ case "$reason" in
+ 			    if_metric=$((if_metric+1))
+ 			fi
+ 		    done
++	    else
++		set_rfc3442_classless_routes
+ 	    fi
+         fi
+ 
+-- 
+2.47.3
+
diff --git a/debian/patches/series b/debian/patches/series
index 8d5d62a..47c3558 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -6,3 +6,4 @@ conf-env-split-bpo/0002-api_extensions-add-environment_runtime_hooks-extensi.pat
 conf-env-split-bpo/0003-doc-add-lxc.environment.-runtime-hooks.patch
 pve/0001-PVE-Config-deny-rw-mounting-of-sys-and-proc.patch
 pve/0002-PVE-Config-attach-always-use-getent.patch
+pve/0003-PVE-apply-rfc3442-classless-routes.patch
-- 
2.47.3



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