syscall: implement nametomib for openbsd.
Move the existing darwin/freebsd specific nametomib implementation
into the respective operating system dependent files.
Provide a nametomib implementation for openbsd, which operates on a
sysctl MIB that has been pre-generated from the various system headers
by mksysctl_openbsd.pl.
R=rsc
CC=golang-dev
https://golang.org/cl/4935044
diff --git a/src/pkg/syscall/syscall_freebsd.go b/src/pkg/syscall/syscall_freebsd.go
index b041357..4962c74 100644
--- a/src/pkg/syscall/syscall_freebsd.go
+++ b/src/pkg/syscall/syscall_freebsd.go
@@ -28,6 +28,31 @@
raw RawSockaddrDatalink
}
+// Translate "kern.hostname" to []_C_int{0,1,2,3}.
+func nametomib(name string) (mib []_C_int, err error) {
+ const siz = unsafe.Sizeof(mib[0])
+
+ // NOTE(rsc): It seems strange to set the buffer to have
+ // size CTL_MAXNAME+2 but use only CTL_MAXNAME
+ // as the size. I don't know why the +2 is here, but the
+ // kernel uses +2 for its own implementation of this function.
+ // I am scared that if we don't include the +2 here, the kernel
+ // will silently write 2 words farther than we specify
+ // and we'll get memory corruption.
+ var buf [CTL_MAXNAME + 2]_C_int
+ n := uintptr(CTL_MAXNAME) * siz
+
+ p := (*byte)(unsafe.Pointer(&buf[0]))
+ bytes := StringByteSlice(name)
+
+ // Magic sysctl: "setting" 0.3 to a string name
+ // lets you read back the array of integers form.
+ if err = sysctl([]_C_int{0, 3}, p, &n, &bytes[0], uintptr(len(name))); err != nil {
+ return nil, err
+ }
+ return buf[0 : n/siz], nil
+}
+
// ParseDirent parses up to max directory entries in buf,
// appending the names to names. It returns the number
// bytes consumed from buf, the number of entries added
