ignore errors in setsockopt on old kernels

mtprotoproxy.py

@@ -639,24 +639,31 @@ async def handle_handshake(reader, writer):
     return False
 
 
+def try_setsockopt(sock, level, option, value):
+    try:
+        sock.setsockopt(level, option, value)
+    except OSError as E:
+        pass
+
+
 def set_keepalive(sock, interval=40, attempts=5):
     sock.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
     if hasattr(socket, "TCP_KEEPIDLE"):
-        sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPIDLE, interval)
+        try_setsockopt(sock, socket.IPPROTO_TCP, socket.TCP_KEEPIDLE, interval)
     if hasattr(socket, "TCP_KEEPINTVL"):
-        sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPINTVL, interval)
+        try_setsockopt(sock, socket.IPPROTO_TCP, socket.TCP_KEEPINTVL, interval)
     if hasattr(socket, "TCP_KEEPCNT"):
-        sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPCNT, attempts)
+        try_setsockopt(sock, socket.IPPROTO_TCP, socket.TCP_KEEPCNT, attempts)
 
 
 def set_ack_timeout(sock, timeout):
     if hasattr(socket, "TCP_USER_TIMEOUT"):
-        sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_USER_TIMEOUT, timeout*1000)
+        try_setsockopt(sock, socket.IPPROTO_TCP, socket.TCP_USER_TIMEOUT, timeout*1000)
 
 
 def set_bufsizes(sock, recv_buf, send_buf):
-    sock.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, recv_buf)
-    sock.setsockopt(socket.SOL_SOCKET, socket.SO_SNDBUF, send_buf)
+    try_setsockopt(sock, socket.SOL_SOCKET, socket.SO_RCVBUF, recv_buf)
+    try_setsockopt(sock, socket.SOL_SOCKET, socket.SO_SNDBUF, send_buf)
 
 
 async def open_connection_tryer(addr, port, limit, timeout, max_attempts=3):