diff --git a/src/resolve/resolved-resolv-conf.c b/src/resolve/resolved-resolv-conf.c index 5a022507c9..edad569acd 100644 --- a/src/resolve/resolved-resolv-conf.c +++ b/src/resolve/resolved-resolv-conf.c @@ -21,9 +21,49 @@ /* A resolv.conf file containing the domain data we learnt from uplink, but our own DNS server address. */ #define PRIVATE_STUB_RESOLV_CONF "/run/systemd/resolve/stub-resolv.conf" -/* A static resolv.conf file containing no domains, but only our own DNS sever address */ +/* A static resolv.conf file containing no domains, but only our own DNS server address */ #define PRIVATE_STATIC_RESOLV_CONF ROOTLIBEXECDIR "/resolv.conf" +int manager_check_resolv_conf(const Manager *m) { + const char *path; + struct stat st; + int r; + + assert(m); + + /* This warns only when our stub listener is disabled and /etc/resolv.conf is a symlink to + * PRIVATE_STATIC_RESOLV_CONF or PRIVATE_STUB_RESOLV_CONF. */ + + if (m->dns_stub_listener_mode != DNS_STUB_LISTENER_NO) + return 0; + + r = stat("/etc/resolv.conf", &st); + if (r < 0) { + if (errno == ENOENT) + return 0; + + return log_warning_errno(errno, "Failed to stat /etc/resolv.conf: %m"); + } + + FOREACH_STRING(path, + PRIVATE_STUB_RESOLV_CONF, + PRIVATE_STATIC_RESOLV_CONF) { + + struct stat own; + + /* Is it symlinked to our own uplink file? */ + if (stat(path, &own) >= 0 && + st.st_dev == own.st_dev && + st.st_ino == own.st_ino) { + log_warning("In spite of DNSStubListner= is disabled, /etc/resolv.conf is a symlink to %s, " + "which expects DNSStubListner= is enabled.", path); + return -EOPNOTSUPP; + } + } + + return 0; +} + static bool file_is_our_own(const struct stat *st) { const char *path; diff --git a/src/resolve/resolved-resolv-conf.h b/src/resolve/resolved-resolv-conf.h index 105ae4cae8..e60beb40b7 100644 --- a/src/resolve/resolved-resolv-conf.h +++ b/src/resolve/resolved-resolv-conf.h @@ -4,5 +4,6 @@ #include "resolved-manager.h" +int manager_check_resolv_conf(const Manager *m); int manager_read_resolv_conf(Manager *m); int manager_write_resolv_conf(Manager *m); diff --git a/src/resolve/resolved.c b/src/resolve/resolved.c index c01e53e9da..6ff56bc974 100644 --- a/src/resolve/resolved.c +++ b/src/resolve/resolved.c @@ -80,6 +80,8 @@ int main(int argc, char *argv[]) { /* Write finish default resolv.conf to avoid a dangling symlink */ (void) manager_write_resolv_conf(m); + (void) manager_check_resolv_conf(m); + /* Let's drop the remaining caps now */ r = capability_bounding_set_drop(0, true); if (r < 0) {