From 1316ec49f209e31799d42d114bd7f35d5acbe097 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 22 Nov 2022 12:28:19 +0100
Subject: [PATCH] resolved: handle -EINTR returned from fd_wait_for_event()
 better

We might get signals for various reasons (for example, somebody asking
us to reload caches via a signal), hence let's handle this gracefully.

(cherry picked from commit 6d66a221685c15798e796d9738f73fdb1fdccdb2)

Related: #2172846
---
 src/resolve/resolved-manager.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/src/resolve/resolved-manager.c b/src/resolve/resolved-manager.c
index 2a23c387a6..5583d63527 100644
--- a/src/resolve/resolved-manager.c
+++ b/src/resolve/resolved-manager.c
@@ -842,11 +842,14 @@ int manager_recv(Manager *m, int fd, DnsProtocol protocol, DnsPacket **ret) {
 }
 
 static int sendmsg_loop(int fd, struct msghdr *mh, int flags) {
+        usec_t end;
         int r;
 
         assert(fd >= 0);
         assert(mh);
 
+        end = usec_add(now(CLOCK_MONOTONIC), SEND_TIMEOUT_USEC);
+
         for (;;) {
                 if (sendmsg(fd, mh, flags) >= 0)
                         return 0;
@@ -857,20 +860,26 @@ static int sendmsg_loop(int fd, struct msghdr *mh, int flags) {
                 if (errno != EAGAIN)
                         return -errno;
 
-                r = fd_wait_for_event(fd, POLLOUT, SEND_TIMEOUT_USEC);
-                if (r < 0)
+                r = fd_wait_for_event(fd, POLLOUT, LESS_BY(end, now(CLOCK_MONOTONIC)));
+                if (r < 0) {
+                        if (ERRNO_IS_TRANSIENT(r))
+                                continue;
                         return r;
+                }
                 if (r == 0)
                         return -ETIMEDOUT;
         }
 }
 
 static int write_loop(int fd, void *message, size_t length) {
+        usec_t end;
         int r;
 
         assert(fd >= 0);
         assert(message);
 
+        end = usec_add(now(CLOCK_MONOTONIC), SEND_TIMEOUT_USEC);
+
         for (;;) {
                 if (write(fd, message, length) >= 0)
                         return 0;
@@ -881,9 +890,12 @@ static int write_loop(int fd, void *message, size_t length) {
                 if (errno != EAGAIN)
                         return -errno;
 
-                r = fd_wait_for_event(fd, POLLOUT, SEND_TIMEOUT_USEC);
-                if (r < 0)
+                r = fd_wait_for_event(fd, POLLOUT, LESS_BY(end, now(CLOCK_MONOTONIC)));
+                if (r < 0) {
+                        if (ERRNO_IS_TRANSIENT(r))
+                                continue;
                         return r;
+                }
                 if (r == 0)
                         return -ETIMEDOUT;
         }