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/* SPDX-License-Identifier: LGPL-2.1+ */
#include <net/if.h>
#include <stdlib.h>
#include "sd-netlink.h"
#include "loopback-setup.h"
#include "missing.h"
#include "netlink-util.h"
#define LOOPBACK_SETUP_TIMEOUT_USEC (5 * USEC_PER_SEC)
struct state {
unsigned n_messages;
int rcode;
const char *error_message;
const char *success_message;
};
static int generic_handler(sd_netlink *rtnl, sd_netlink_message *m, void *userdata) {
struct state *s = userdata;
int r;
assert(s);
assert(s->n_messages > 0);
s->n_messages--;
errno = 0;
r = sd_netlink_message_get_errno(m);
if (r < 0)
log_debug_errno(r, "%s: %m", s->error_message);
else
log_debug("%s", s->success_message);
s->rcode = r;
return 0;
}
static int start_loopback(sd_netlink *rtnl, struct state *s) {
_cleanup_(sd_netlink_message_unrefp) sd_netlink_message *req = NULL;
int r;
assert(rtnl);
assert(s);
r = sd_rtnl_message_new_link(rtnl, &req, RTM_SETLINK, LOOPBACK_IFINDEX);
if (r < 0)
return r;
r = sd_rtnl_message_link_set_flags(req, IFF_UP, IFF_UP);
if (r < 0)
return r;
r = sd_netlink_call_async(rtnl, NULL, req, generic_handler, NULL, s, LOOPBACK_SETUP_TIMEOUT_USEC, "systemd-start-loopback");
if (r < 0)
return r;
s->n_messages ++;
return 0;
}
static int add_ipv4_address(sd_netlink *rtnl, struct state *s) {
_cleanup_(sd_netlink_message_unrefp) sd_netlink_message *req = NULL;
int r;
assert(rtnl);
assert(s);
r = sd_rtnl_message_new_addr(rtnl, &req, RTM_NEWADDR, LOOPBACK_IFINDEX, AF_INET);
if (r < 0)
return r;
r = sd_rtnl_message_addr_set_prefixlen(req, 8);
if (r < 0)
return r;
r = sd_rtnl_message_addr_set_flags(req, IFA_F_PERMANENT);
if (r < 0)
return r;
r = sd_rtnl_message_addr_set_scope(req, RT_SCOPE_HOST);
if (r < 0)
return r;
r = sd_netlink_message_append_in_addr(req, IFA_LOCAL, &(struct in_addr) { .s_addr = htobe32(INADDR_LOOPBACK) } );
if (r < 0)
return r;
r = sd_netlink_call_async(rtnl, NULL, req, generic_handler, NULL, s, USEC_INFINITY, "systemd-loopback-ipv4");
if (r < 0)
return r;
s->n_messages ++;
return 0;
}
static int add_ipv6_address(sd_netlink *rtnl, struct state *s) {
_cleanup_(sd_netlink_message_unrefp) sd_netlink_message *req = NULL;
int r;
assert(rtnl);
assert(s);
r = sd_rtnl_message_new_addr(rtnl, &req, RTM_NEWADDR, LOOPBACK_IFINDEX, AF_INET6);
if (r < 0)
return r;
r = sd_rtnl_message_addr_set_prefixlen(req, 128);
if (r < 0)
return r;
r = sd_rtnl_message_addr_set_flags(req, IFA_F_PERMANENT);
if (r < 0)
return r;
r = sd_rtnl_message_addr_set_scope(req, RT_SCOPE_HOST);
if (r < 0)
return r;
r = sd_netlink_message_append_in6_addr(req, IFA_LOCAL, &in6addr_loopback);
if (r < 0)
return r;
r = sd_netlink_call_async(rtnl, NULL, req, generic_handler, NULL, s, USEC_INFINITY, "systemd-loopback-ipv6");
if (r < 0)
return r;
s->n_messages ++;
return 0;
}
static bool check_loopback(sd_netlink *rtnl) {
_cleanup_(sd_netlink_message_unrefp) sd_netlink_message *req = NULL, *reply = NULL;
unsigned flags;
int r;
r = sd_rtnl_message_new_link(rtnl, &req, RTM_GETLINK, LOOPBACK_IFINDEX);
if (r < 0)
return false;
r = sd_netlink_call(rtnl, req, USEC_INFINITY, &reply);
if (r < 0)
return false;
r = sd_rtnl_message_link_get_flags(reply, &flags);
if (r < 0)
return false;
return flags & IFF_UP;
}
int loopback_setup(void) {
_cleanup_(sd_netlink_unrefp) sd_netlink *rtnl = NULL;
struct state state_4 = {
.error_message = "Failed to add address 127.0.0.1 to loopback interface",
.success_message = "Successfully added address 127.0.0.1 to loopback interface",
}, state_6 = {
.error_message = "Failed to add address ::1 to loopback interface",
.success_message = "Successfully added address ::1 to loopback interface",
}, state_up = {
.error_message = "Failed to bring loopback interface up",
.success_message = "Successfully brought loopback interface up",
};
int r;
r = sd_netlink_open(&rtnl);
if (r < 0)
return log_error_errno(r, "Failed to open netlink: %m");
/* Note that we add the IP addresses here explicitly even though the kernel does that too implicitly when
* setting up the loopback device. The reason we do this here a second time (and possibly race against the
* kernel) is that we want to synchronously wait until the IP addresses are set up correctly, see
*
* https://github.com/systemd/systemd/issues/5641 */
r = add_ipv4_address(rtnl, &state_4);
if (r < 0)
return log_error_errno(r, "Failed to enqueue IPv4 loopback address add request: %m");
r = add_ipv6_address(rtnl, &state_6);
if (r < 0)
return log_error_errno(r, "Failed to enqueue IPv6 loopback address add request: %m");
r = start_loopback(rtnl, &state_up);
if (r < 0)
return log_error_errno(r, "Failed to enqueue loopback interface start request: %m");
while (state_4.n_messages + state_6.n_messages + state_up.n_messages > 0) {
r = sd_netlink_wait(rtnl, LOOPBACK_SETUP_TIMEOUT_USEC);
if (r < 0)
return log_error_errno(r, "Failed to wait for netlink event: %m");
r = sd_netlink_process(rtnl, NULL);
if (r < 0)
return log_warning_errno(r, "Failed to process netlink event: %m");
}
/* Note that we don't really care whether the addresses could be added or not */
if (state_up.rcode != 0) {
/* If we lack the permissions to configure the loopback device,
* but we find it to be already configured, let's exit cleanly,
* in order to supported unprivileged containers. */
if (state_up.rcode == -EPERM && check_loopback(rtnl))
return 0;
return log_warning_errno(state_up.rcode, "Failed to configure loopback device: %m");
}
return 0;
}
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