uevent: increase netlink buffer sizes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 14 insertions, 10 deletions

diff --git a/util-linux/uevent.c b/util-linux/uevent.c
index 57d9328ef..2f1135f0c 100644
--- a/util-linux/uevent.c
+++ b/util-linux/uevent.c
@@ -26,8 +26,6 @@
 #include "common_bufsiz.h"
 #include <linux/netlink.h>
 
-#define BUFFER_SIZE 16*1024
-
 #define env ((char **)bb_common_bufsiz1)
 #define INIT_G() do { setup_common_bufsiz(); } while (0)
 enum {
@@ -37,10 +35,16 @@ enum {
          */
 };
 
-#ifndef SO_RCVBUFFORCE
-#define SO_RCVBUFFORCE 33
-#endif
-enum { RCVBUF = 2 * 1024 * 1024 };
+enum {
+        /* socket receive buffer of 2MiB proved to be too small:
+         * http://lists.busybox.net/pipermail/busybox/2019-December/087665.html
+         * Udevd seems to use a whooping 128MiB.
+         * The socket receive buffer size is just a resource limit.
+         * The buffers are allocated lazily so the memory is not wasted.
+         */
+        KERN_RCVBUF = 128 * 1024 * 1024,
+        USER_RCVBUF = 16 * 1024,
+};
 
 int uevent_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int uevent_main(int argc UNUSED_PARAM, char **argv)
@@ -57,7 +61,7 @@ int uevent_main(int argc UNUSED_PARAM, char **argv)
         // Reproducer:
         //      uevent mdev &
         //      find /sys -name uevent -exec sh -c 'echo add >"{}"' ';'
-        fd = create_and_bind_to_netlink(NETLINK_KOBJECT_UEVENT, /*groups:*/ 1 << 0, RCVBUF);
+        fd = create_and_bind_to_netlink(NETLINK_KOBJECT_UEVENT, /*groups:*/ 1 << 0, KERN_RCVBUF);
 
         for (;;) {
                 char *netbuf;
@@ -69,7 +73,7 @@ int uevent_main(int argc UNUSED_PARAM, char **argv)
                 // for a new uevent notification to come in.
                 // We use a fresh mmap so that buffer is not allocated
                 // until kernel actually starts filling it.
-                netbuf = mmap(NULL, BUFFER_SIZE,
+                netbuf = mmap(NULL, USER_RCVBUF,
                                         PROT_READ | PROT_WRITE,
                                         MAP_PRIVATE | MAP_ANON,
                                         /* ignored: */ -1, 0);
@@ -77,7 +81,7 @@ int uevent_main(int argc UNUSED_PARAM, char **argv)
                         bb_simple_perror_msg_and_die("mmap");
 
                 // Here we block, possibly for a very long time
-                len = safe_read(fd, netbuf, BUFFER_SIZE - 1);
+                len = safe_read(fd, netbuf, USER_RCVBUF - 1);
                 if (len < 0)
                         bb_simple_perror_msg_and_die("read");
                 end = netbuf + len;
@@ -108,7 +112,7 @@ int uevent_main(int argc UNUSED_PARAM, char **argv)
                         while (env[idx])
                                 bb_unsetenv(env[idx++]);
                 }
-                munmap(netbuf, BUFFER_SIZE);
+                munmap(netbuf, USER_RCVBUF);
         }
 
         return 0; // not reached