/* SPDX-License-Identifier: LGPL-2.1+ */ #include #include #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); 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); 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); 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; }