From 0a377494bcfcf4e145e260478071be124d56dc6d Mon Sep 17 00:00:00 2001

From: Yu Watanabe <watanabe.yu+github@gmail.com>

Date: Fri, 20 Aug 2021 09:41:34 +0900

Subject: [PATCH] network: add UseMTU= in [IPv6AcceptRA]

Note that kernel has similar knob in sysctl: accept_ra_mtu.

Closes #18868.

---

 man/systemd.network.xml                          |  8 ++++++++

 src/network/networkd-ndisc.c                     | 14 +++++++-------

 src/network/networkd-network-gperf.gperf         |  1 +

 src/network/networkd-network.c                   |  3 ++-

 src/network/networkd-network.h                   |  1 +

 test/fuzz/fuzz-network-parser/directives.network |  1 +

 6 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/man/systemd.network.xml b/man/systemd.network.xml

index 03100c035b84..573ba959eb4d 100644

--- a/man/systemd.network.xml

+++ b/man/systemd.network.xml

@@ -2265,6 +2265,14 @@ IPv6Token=prefixstable:2002:da8:1::</programlisting></para>

           </listitem>

         </varlistentry>

+        <varlistentry>

+          <term><varname>UseMTU=</varname></term>

+          <listitem>

+            <para>Takes a boolean. When true, the MTU received in the Router Advertisement will be

+            used. Defaults to true.</para>

+          </listitem>

+        </varlistentry>

+

         <varlistentry>

           <term><varname>UseAutonomousPrefix=</varname></term>

           <listitem>

diff --git a/src/network/networkd-ndisc.c b/src/network/networkd-ndisc.c

index f58edb8f3cae..fe1f1e0333cf 100644

--- a/src/network/networkd-ndisc.c

+++ b/src/network/networkd-ndisc.c

@@ -536,9 +536,9 @@ static int ndisc_request_address(Address *in, Link *link, sd_ndisc_router *rt) {

 static int ndisc_router_process_default(Link *link, sd_ndisc_router *rt) {

         _cleanup_(route_freep) Route *route = NULL;

         struct in6_addr gateway;

-        uint16_t lifetime;

+        uint32_t table, mtu = 0;

         unsigned preference;

-        uint32_t table, mtu;

+        uint16_t lifetime;

         usec_t time_now;

         int r;

@@ -575,11 +575,11 @@ static int ndisc_router_process_default(Link *link, sd_ndisc_router *rt) {

         if (r < 0)

                 return log_link_error_errno(link, r, "Failed to get RA timestamp: %m");

-        r = sd_ndisc_router_get_mtu(rt, &mtu);

-        if (r == -ENODATA)

-                mtu = 0;

-        else if (r < 0)

-                return log_link_error_errno(link, r, "Failed to get default router MTU from RA: %m");

+        if (link->network->ipv6_accept_ra_use_mtu) {

+                r = sd_ndisc_router_get_mtu(rt, &mtu);

+                if (r < 0 && r != -ENODATA)

+                        return log_link_error_errno(link, r, "Failed to get default router MTU from RA: %m");

+        }

         table = link_get_ipv6_accept_ra_route_table(link);

diff --git a/src/network/networkd-network-gperf.gperf b/src/network/networkd-network-gperf.gperf

index aa4dc00e55bc..846e54aed759 100644

--- a/src/network/networkd-network-gperf.gperf

+++ b/src/network/networkd-network-gperf.gperf

@@ -256,6 +256,7 @@ IPv6AcceptRA.UseAutonomousPrefix,            config_parse_bool,

 IPv6AcceptRA.UseOnLinkPrefix,                config_parse_bool,                                        0,                             offsetof(Network, ipv6_accept_ra_use_onlink_prefix)

 IPv6AcceptRA.UseDNS,                         config_parse_bool,                                        0,                             offsetof(Network, ipv6_accept_ra_use_dns)

 IPv6AcceptRA.UseDomains,                     config_parse_ipv6_accept_ra_use_domains,                  0,                             offsetof(Network, ipv6_accept_ra_use_domains)

+IPv6AcceptRA.UseMTU,                         config_parse_bool,                                        0,                             offsetof(Network, ipv6_accept_ra_use_mtu)

 IPv6AcceptRA.DHCPv6Client,                   config_parse_ipv6_accept_ra_start_dhcp6_client,           0,                             offsetof(Network, ipv6_accept_ra_start_dhcp6_client)

 IPv6AcceptRA.RouteTable,                     config_parse_section_route_table,                         0,                             0

 IPv6AcceptRA.RouteMetric,                    config_parse_dhcp_route_metric,                           0,                             0

diff --git a/src/network/networkd-network.c b/src/network/networkd-network.c

index bb09ba9e8933..1928db537e0c 100644

--- a/src/network/networkd-network.c

+++ b/src/network/networkd-network.c

@@ -400,15 +400,16 @@ int network_load_one(Manager *manager, OrderedHashmap **networks, const char *fi

                 .ipv4_accept_local = -1,

                 .ipv4_route_localnet = -1,

                 .ipv6_privacy_extensions = IPV6_PRIVACY_EXTENSIONS_NO,

-                .ipv6_accept_ra = -1,

                 .ipv6_dad_transmits = -1,

                 .ipv6_hop_limit = -1,

                 .ipv6_proxy_ndp = -1,

                 .proxy_arp = -1,

+                .ipv6_accept_ra = -1,

                 .ipv6_accept_ra_use_dns = true,

                 .ipv6_accept_ra_use_autonomous_prefix = true,

                 .ipv6_accept_ra_use_onlink_prefix = true,

+                .ipv6_accept_ra_use_mtu = true,

                 .ipv6_accept_ra_route_table = RT_TABLE_MAIN,

                 .ipv6_accept_ra_route_metric = DHCP_ROUTE_METRIC,

                 .ipv6_accept_ra_start_dhcp6_client = IPV6_ACCEPT_RA_START_DHCP6_CLIENT_YES,

diff --git a/src/network/networkd-network.h b/src/network/networkd-network.h

index 815bcf5023fc..95c86e723040 100644

--- a/src/network/networkd-network.h

+++ b/src/network/networkd-network.h

@@ -301,6 +301,7 @@ struct Network {

         bool ipv6_accept_ra_use_dns;

         bool ipv6_accept_ra_use_autonomous_prefix;

         bool ipv6_accept_ra_use_onlink_prefix;

+        bool ipv6_accept_ra_use_mtu;

         bool active_slave;

         bool primary_slave;

         DHCPUseDomains ipv6_accept_ra_use_domains;

diff --git a/test/fuzz/fuzz-network-parser/directives.network b/test/fuzz/fuzz-network-parser/directives.network

index 8fe4ced35154..a3711cb77d9c 100644

--- a/test/fuzz/fuzz-network-parser/directives.network

+++ b/test/fuzz/fuzz-network-parser/directives.network

@@ -342,6 +342,7 @@ Label=

 Prefix=

 [IPv6AcceptRA]

 UseDomains=

+UseMTU=

 RouteTable=

 RouteMetric=

 UseDNS=