rpc: avoid use of cgo by hard-coding maxPathSize

Implemented ethereum/go-ethereum#27447

rpc/server/ipc_unix.go

@@ -15,6 +15,7 @@
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
 //go:build darwin || dragonfly || freebsd || linux || nacl || netbsd || openbsd || solaris
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris
 
 package server
 
@@ -28,10 +29,17 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 )
 
+const (
+	// On Linux, sun_path is 108 bytes in size
+	// see http://man7.org/linux/man-pages/man7/unix.7.html
+	maxPathSize = int(108)
+)
+
 // ipcListen will create a Unix socket on the given endpoint.
 func ipcListen(endpoint string) (net.Listener, error) {
-	if len(endpoint) > int(max_path_size) {
-		log.Warn(fmt.Sprintf("The ipc endpoint is longer than %d characters. ", max_path_size),
+	// account for null-terminator too
+	if len(endpoint)+1 > maxPathSize {
+		log.Warn(fmt.Sprintf("The ipc endpoint is longer than %d characters. ", maxPathSize-1),
 			"endpoint", endpoint)
 	}