From 36d892b7e6753dfc67110b57c55864647a04c5cb Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 6 Nov 2020 14:56:16 +0100
Subject: [PATCH] resolved: use stat_inode_unmodified() to detect /etc/hosts
 changes

---
 src/resolve/resolved-etc-hosts.c | 14 +++++---------
 src/resolve/resolved-manager.c   |  3 ---
 src/resolve/resolved-manager.h   |  5 ++---
 3 files changed, 7 insertions(+), 15 deletions(-)

diff --git a/src/resolve/resolved-etc-hosts.c b/src/resolve/resolved-etc-hosts.c
index e784213e91..dda2014017 100644
--- a/src/resolve/resolved-etc-hosts.c
+++ b/src/resolve/resolved-etc-hosts.c
@@ -10,6 +10,7 @@
 #include "resolved-dns-synthesize.h"
 #include "resolved-etc-hosts.h"
 #include "socket-netlink.h"
+#include "stat-util.h"
 #include "string-util.h"
 #include "strv.h"
 #include "time-util.h"
@@ -36,9 +37,7 @@ void etc_hosts_free(EtcHosts *hosts) {
 
 void manager_etc_hosts_flush(Manager *m) {
         etc_hosts_free(&m->etc_hosts);
-        m->etc_hosts_mtime = USEC_INFINITY;
-        m->etc_hosts_ino = 0;
-        m->etc_hosts_dev = 0;
+        m->etc_hosts_stat = (struct stat) {};
 }
 
 static int parse_line(EtcHosts *hosts, unsigned nr, const char *line) {
@@ -214,7 +213,7 @@ static int manager_etc_hosts_read(Manager *m) {
 
         m->etc_hosts_last = ts;
 
-        if (m->etc_hosts_mtime != USEC_INFINITY) {
+        if (m->etc_hosts_stat.st_mode != 0) {
                 if (stat("/etc/hosts", &st) < 0) {
                         if (errno != ENOENT)
                                 return log_error_errno(errno, "Failed to stat /etc/hosts: %m");
@@ -224,8 +223,7 @@ static int manager_etc_hosts_read(Manager *m) {
                 }
 
                 /* Did the mtime or ino/dev change? If not, there's no point in re-reading the file. */
-                if (timespec_load(&st.st_mtim) == m->etc_hosts_mtime &&
-                    st.st_ino == m->etc_hosts_ino && st.st_dev == m->etc_hosts_dev)
+                if (stat_inode_unmodified(&m->etc_hosts_stat, &st))
                         return 0;
         }
 
@@ -248,9 +246,7 @@ static int manager_etc_hosts_read(Manager *m) {
         if (r < 0)
                 return r;
 
-        m->etc_hosts_mtime = timespec_load(&st.st_mtim);
-        m->etc_hosts_ino = st.st_ino;
-        m->etc_hosts_dev = st.st_dev;
+        m->etc_hosts_stat = st;
         m->etc_hosts_last = ts;
 
         return 1;
diff --git a/src/resolve/resolved-manager.c b/src/resolve/resolved-manager.c
index d721e76749..81d043a3fa 100644
--- a/src/resolve/resolved-manager.c
+++ b/src/resolve/resolved-manager.c
@@ -641,9 +641,6 @@ int manager_new(Manager **ret) {
                 .read_resolv_conf = true,
                 .need_builtin_fallbacks = true,
                 .etc_hosts_last = USEC_INFINITY,
-                .etc_hosts_mtime = USEC_INFINITY,
-                .etc_hosts_ino = 0,
-                .etc_hosts_dev = 0,
                 .read_etc_hosts = true,
         };
 
diff --git a/src/resolve/resolved-manager.h b/src/resolve/resolved-manager.h
index 120b63dc8c..5471b20ff9 100644
--- a/src/resolve/resolved-manager.h
+++ b/src/resolve/resolved-manager.h
@@ -129,9 +129,8 @@ struct Manager {
 
         /* Data from /etc/hosts */
         EtcHosts etc_hosts;
-        usec_t etc_hosts_last, etc_hosts_mtime;
-        ino_t etc_hosts_ino;
-        dev_t etc_hosts_dev;
+        usec_t etc_hosts_last;
+        struct stat etc_hosts_stat;
         bool read_etc_hosts;
 
         OrderedSet *dns_extra_stub_listeners;