internal/netlink: set receive buffer size

This is done by both systemd sd-device and AOSP ueventd to improve robustness. Rosa OS will still handle ENOBUFS via coldboot but a big buffer should mitigate this as well.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/netlink/netlink.go

@@ -46,7 +46,11 @@ type Conn struct {
 
 // Dial returns the address of a newly connected generic netlink connection of
 // specified family and groups.
-func Dial(family int, groups uint32) (*Conn, error) {
+//
+// For a nonzero rcvbuf, the socket receive buffer size is set to its absolute
+// value via SO_RCVBUF for a positive value, or SO_RCVBUFFORCE for a negative
+// value.
+func Dial(family int, groups uint32, rcvbuf int64) (*Conn, error) {
 	var c Conn
 	if fd, err := syscall.Socket(
 		syscall.AF_NETLINK,
@@ -75,6 +79,23 @@ func Dial(family int, groups uint32) (*Conn, error) {
 			return nil, syscall.ENOTRECOVERABLE
 		}
 
+		if rcvbuf != 0 {
+			opt := syscall.SO_RCVBUF
+			if rcvbuf < 0 {
+				opt = syscall.SO_RCVBUFFORCE
+				rcvbuf = -rcvbuf
+			}
+			if err = syscall.SetsockoptInt(
+				fd,
+				syscall.SOL_SOCKET,
+				opt,
+				int(rcvbuf),
+			); err != nil {
+				_ = syscall.Close(fd)
+				return nil, os.NewSyscallError("setsockopt", err)
+			}
+		}
+
 		c.family = family
 		c.f = os.NewFile(uintptr(fd), "netlink")
 		if c.raw, err = c.f.SyscallConn(); err != nil {