[systemd-devel] [PATCH] networkd: add preferred source to dhcp4 gateway route

[Emil Renner Berthing]

This makes DHCPv4 and IPv4LL coexist peacefully.
---
 src/network/networkd-dhcp4.c | 11 +++++++++++
 src/network/networkd-route.c | 22 ++++++++++++++++++++++
 src/network/networkd.h       |  2 ++
 3 files changed, 35 insertions(+)

diff --git a/src/network/networkd-dhcp4.c b/src/network/networkd-dhcp4.c
index 5e4ff2b..748db09 100644
--- a/src/network/networkd-dhcp4.c
+++ b/src/network/networkd-dhcp4.c
@@ -67,9 +67,18 @@ static int link_set_dhcp_routes(Link *link) {
                 return r;
         }
         if (r >= 0) {
+                struct in_addr address;
                 _cleanup_route_free_ Route *route = NULL;
                 _cleanup_route_free_ Route *route_gw = NULL;
 
+                r = sd_dhcp_lease_get_address(link->dhcp_lease, &address);
+                if (r < 0) {
+                        log_warning_link(link,
+                                         "DHCP error: could not get address: %s",
+                                         strerror(-r));
+                        return r;
+                }
+
                 r = route_new_dynamic(&route, RTPROT_DHCP);
                 if (r < 0) {
                         log_error_link(link,
@@ -92,6 +101,8 @@ static int link_set_dhcp_routes(Link *link) {
                 route_gw->family = AF_INET;
                 route_gw->dst_addr.in = gateway;
                 route_gw->dst_prefixlen = 32;
+                route_gw->prefsrc_addr.in = address;
+                route_gw->prefsrc_set = 1;
                 route_gw->scope = RT_SCOPE_LINK;
                 route_gw->metrics = DHCP_ROUTE_METRIC;
 
diff --git a/src/network/networkd-route.c b/src/network/networkd-route.c
index aead4fb..c4be3f4 100644
--- a/src/network/networkd-route.c
+++ b/src/network/networkd-route.c
@@ -144,6 +144,17 @@ int route_drop(Route *route, Link *link,
                 }
         }
 
+        if (route->prefsrc_set) {
+                if (route->family == AF_INET)
+                        r = sd_rtnl_message_append_in_addr(req, RTA_PREFSRC, &route->prefsrc_addr.in);
+                else if (route->family == AF_INET6)
+                        r = sd_rtnl_message_append_in6_addr(req, RTA_PREFSRC, &route->prefsrc_addr.in6);
+                if (r < 0) {
+                        log_error("Could not append RTA_PREFSRC attribute: %s", strerror(-r));
+                        return r;
+                }
+        }
+
         r = sd_rtnl_message_route_set_scope(req, route->scope);
         if (r < 0) {
                 log_error("Could not set scope: %s", strerror(-r));
@@ -218,6 +229,17 @@ int route_configure(Route *route, Link *link,
                 }
         }
 
+        if (route->prefsrc_set) {
+                if (route->family == AF_INET)
+                        r = sd_rtnl_message_append_in_addr(req, RTA_PREFSRC, &route->prefsrc_addr.in);
+                else if (route->family == AF_INET6)
+                        r = sd_rtnl_message_append_in6_addr(req, RTA_PREFSRC, &route->prefsrc_addr.in6);
+                if (r < 0) {
+                        log_error("Could not append RTA_PREFSRC attribute: %s", strerror(-r));
+                        return r;
+                }
+        }
+
         r = sd_rtnl_message_route_set_scope(req, route->scope);
         if (r < 0) {
                 log_error("Could not set scope: %s", strerror(-r));
diff --git a/src/network/networkd.h b/src/network/networkd.h
index ab5df1a..b32eb31 100644
--- a/src/network/networkd.h
+++ b/src/network/networkd.h
@@ -144,12 +144,14 @@ struct Route {
 
         int family;
         unsigned char dst_prefixlen;
+        unsigned char prefsrc_set;
         unsigned char scope;
         uint32_t metrics;
         unsigned char protocol;  /* RTPROT_* */
 
         union in_addr_union in_addr;
         union in_addr_union dst_addr;
+        union in_addr_union prefsrc_addr;
 
         LIST_FIELDS(Route, routes);
 };
-- 
2.1.0