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network: dhcp4: also support semi-static routes with Gateway=_dhcp4 when UseGateway=no or UseRoutes=no

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This makes the default gateway is read from classless static routes or
router option even if UseGateway=no or UseRoutes=no, and will be used
when configuring semi-static routes such that specified with Gateway=_dhcp4.

This also changes the behavior of RoutesToDNS= or RoutesToNTP=.
Previously, the DNS or NTP servers are not in the same network, then the
routes to the servers were not configured when UseGateway=no or
UseRoutes=no. With this commit, the default gateway in classless static
routes or router option will used to connecting the servers even if
UseGateway=no or UseRoutes=no.

Fixes #20208.
This commit is contained in:
Yu Watanabe 2021-07-13 01:06:08 +09:00
parent 77976a6877
commit 0ebab55f4f
1 changed files with 80 additions and 11 deletions
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91
src/network/networkd-dhcp4.c
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@ -379,9 +379,6 @@ static int dhcp4_request_static_routes(Link *link, struct in_addr *ret_default_g
assert(link->dhcp_lease);
assert(ret_default_gw);
if (!link->network->dhcp_use_routes)
return 0;
n = sd_dhcp_lease_get_routes(link->dhcp_lease, &static_routes);
if (IN_SET(n, 0, -ENODATA)) {
log_link_debug(link, "DHCP: No static routes received from DHCP server.");
@ -406,6 +403,45 @@ static int dhcp4_request_static_routes(Link *link, struct in_addr *ret_default_g
if (classless_route && static_route)
log_link_debug(link, "Classless static routes received from DHCP server: ignoring static-route option");
if (!link->network->dhcp_use_routes) {
if (!classless_route)
return 0;
/* Even if UseRoutes=no, try to find default gateway to make semi-static routes and
* routes to DNS or NTP servers can be configured in later steps. */
for (int i = 0; i < n; i++) {
struct in_addr dst;
uint8_t prefixlen;
if (sd_dhcp_route_get_option(static_routes[i]) != SD_DHCP_OPTION_CLASSLESS_STATIC_ROUTE)
continue;
r = sd_dhcp_route_get_destination(static_routes[i], &dst);
if (r < 0)
return r;
if (in4_addr_is_set(&dst))
continue;
r = sd_dhcp_route_get_destination_prefix_length(static_routes[i], &prefixlen);
if (r < 0)
return r;
if (prefixlen != 0)
continue;
r = sd_dhcp_route_get_gateway(static_routes[i], ret_default_gw);
if (r < 0)
return r;
break;
}
/* Do not return 1 here, to ensure the router option can override the default gateway
* that was found. */
return 0;
}
for (int i = 0; i < n; i++) {
_cleanup_(route_freep) Route *route = NULL;
struct in_addr gw;
@ -454,19 +490,15 @@ static int dhcp4_request_static_routes(Link *link, struct in_addr *ret_default_g
return classless_route;
}
static int dhcp4_request_gateway(Link *link, struct in_addr *ret_gw) {
static int dhcp4_request_gateway(Link *link, struct in_addr *gw) {
_cleanup_(route_freep) Route *route = NULL;
const struct in_addr *router;
struct in_addr address;
Route *rt;
int r;
assert(link);
assert(link->dhcp_lease);
assert(ret_gw);
if (!link->network->dhcp_use_gateway)
return 0;
assert(gw);
r = sd_dhcp_lease_get_address(link->dhcp_lease, &address);
if (r < 0)
@ -484,6 +516,16 @@ static int dhcp4_request_gateway(Link *link, struct in_addr *ret_gw) {
return 0;
}
if (!link->network->dhcp_use_gateway) {
/* When no classless static route is provided, even if UseGateway=no, use the gateway
* address to configure semi-static routes or routes to DNS or NTP servers. Note, if
* neither UseRoutes= nor UseGateway= is disabled, use the default gateway in classless
* static routes if provided (in that case, in4_addr_is_null(gw) below is true). */
if (in4_addr_is_null(gw))
*gw = router[0];
return 0;
}
/* The dhcp netmask may mask out the gateway. First, add an explicit route for the gateway host
* so that we can route no matter the netmask or existing kernel route tables. */
r = dhcp4_request_route_to_gateway(link, &router[0]);
@ -508,18 +550,42 @@ static int dhcp4_request_gateway(Link *link, struct in_addr *ret_gw) {
if (r < 0)
return r;
/* When no classless static route is provided, or UseRoutes=no, then use the router address to
* configure semi-static routes and routes to DNS or NTP servers in later steps. */
*gw = router[0];
return 0;
}
static int dhcp4_request_semi_static_routes(Link *link, const struct in_addr *gw) {
Route *rt;
int r;
assert(link);
assert(link->dhcp_lease);
assert(link->network);
assert(gw);
if (in4_addr_is_null(gw))
return 0;
HASHMAP_FOREACH(rt, link->network->routes_by_section) {
_cleanup_(route_freep) Route *route = NULL;
if (!rt->gateway_from_dhcp_or_ra)
continue;
if (rt->gw_family != AF_INET)
continue;
r = dhcp4_request_route_to_gateway(link, gw);
if (r < 0)
return r;
r = route_dup(rt, &route);
if (r < 0)
return r;
route->gw.in = router[0];
route->gw.in = *gw;
if (!route->protocol_set)
route->protocol = RTPROT_DHCP;
if (!route->priority_set)
@ -534,7 +600,6 @@ static int dhcp4_request_gateway(Link *link, struct in_addr *ret_gw) {
return r;
}
*ret_gw = router[0];
return 0;
}
@ -653,6 +718,10 @@ static int dhcp4_request_routes(Link *link) {
return log_link_error_errno(link, r, "DHCP error: Could not request gateway: %m");
}
r = dhcp4_request_semi_static_routes(link, &gw);
if (r < 0)
return log_link_error_errno(link, r, "DHCP error: Could not request routes with Gateway=_dhcp4 setting: %m");
r = dhcp4_request_routes_to_dns(link, &gw);
if (r < 0)
return log_link_error_errno(link, r, "DHCP error: Could not request routes to DNS servers: %m");