1002-sd-netlink-make-the-default-timeout-configurable-by-.patch

From 5e518008b9015ced364e92648ad17f51e95442bc Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Sun, 1 Oct 2023 12:04:59 +0900
Subject: [PATCH] sd-netlink: make the default timeout configurable by
 environment variable

On normal systems, triggering a timeout should be a bug in code or
configuration error, so I do not think we should extend the default
timeout. Also, we should not introduce a 'first class' configuration
option about that. But, making it configurable may be useful for cases
such that "an extremely highly utilized system (lots of OOM kills,
very high CPU utilization, etc)".

Closes #25441.
---
 docs/ENVIRONMENT.md                    |  3 +++
 src/libsystemd/sd-netlink/sd-netlink.c | 23 +++++++++++++++++++++--
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/docs/ENVIRONMENT.md b/docs/ENVIRONMENT.md
index 1e7a75a36c..81b3c36d58 100644
--- a/docs/ENVIRONMENT.md
+++ b/docs/ENVIRONMENT.md
@@ -108,6 +108,9 @@ All tools:
   for example in `systemd-nspawn`, will be logged to the audit log, if the
   kernel supports this.
 
+* `$SYSTEMD_NETLINK_DEFAULT_TIMEOUT` — specifies the default timeout of waiting
+  replies for netlink messages from the kernel. Defaults to 25 seconds.
+
 `systemctl`:
 
 * `$SYSTEMCTL_FORCE_BUS=1` — if set, do not connect to PID 1's private D-Bus
diff --git a/src/libsystemd/sd-netlink/sd-netlink.c b/src/libsystemd/sd-netlink/sd-netlink.c
index 01a04eb308..dd74a1aa78 100644
--- a/src/libsystemd/sd-netlink/sd-netlink.c
+++ b/src/libsystemd/sd-netlink/sd-netlink.c
@@ -417,8 +417,27 @@ int sd_netlink_process(sd_netlink *nl, sd_netlink_message **ret) {
 }
 
 static usec_t timespan_to_timestamp(usec_t usec) {
-        if (usec == 0)
-                usec = NETLINK_DEFAULT_TIMEOUT_USEC;
+        static bool default_timeout_set = false;
+        static usec_t default_timeout;
+        int r;
+
+        if (usec == 0) {
+                if (!default_timeout_set) {
+                        const char *e;
+
+                        default_timeout_set = true;
+                        default_timeout = NETLINK_DEFAULT_TIMEOUT_USEC;
+
+                        e = getenv("SYSTEMD_NETLINK_DEFAULT_TIMEOUT");
+                        if (e) {
+                                r = parse_sec(e, &default_timeout);
+                                if (r < 0)
+                                        log_debug_errno(r, "sd-netlink: Failed to parse $SYSTEMD_NETLINK_DEFAULT_TIMEOUT environment variable, ignoring: %m");
+                        }
+                }
+
+                usec = default_timeout;
+        }
 
         return usec_add(now(CLOCK_MONOTONIC), usec);
 }
-- 
2.38.1