netconsole

#!/usr/bin/env python3
import sys, socket, threading, ctypes, ctypes.util

_getifaddrs = ctypes.CDLL(ctypes.util.find_library('c')).getifaddrs
_freeifaddrs = ctypes.CDLL(ctypes.util.find_library('c')).freeifaddrs
_inet_ntoa = ctypes.CDLL(ctypes.util.find_library('c')).inet_ntoa
_inet_ntoa.restype = ctypes.c_char_p

in_addr_t = ctypes.c_uint32

class struct_in_addr(ctypes.Structure):
    _fields_ = [('s_addr', in_addr_t)]

if sys.platform == 'darwin':
    sa_family_t = ctypes.c_uint8
    
    class struct_sockaddr(ctypes.Structure):
        _fields_ = [('sa_len', ctypes.c_uint8),
                    ('sa_family', sa_family_t),
                    ('sa_data', ctypes.c_byte * 14),]

    class struct_sockaddr_in(ctypes.Structure):
        _fields_ = [('sin_len', ctypes.c_uint8),
                    ('sin_family', sa_family_t),
                    ('sin_port', ctypes.c_uint16),
                    ('sin_addr', struct_in_addr),
                    ('sin_zero', ctypes.c_char * 8)]

else:
    sa_family_t = ctypes.c_ushort
    
    class struct_sockaddr(ctypes.Structure):
        _fields_ = [('sa_family', ctypes.c_ushort),
                    ('sa_data', ctypes.c_byte * 14),]

    class struct_sockaddr_in(ctypes.Structure):
        _fields_ = [('sin_family', sa_family_t),
                    ('sin_port', ctypes.c_uint16),
                    ('sin_addr', struct_in_addr)]

class struct_ifaddrs(ctypes.Structure):
    pass
struct_ifaddrs._fields_ = [('ifa_next', ctypes.POINTER(struct_ifaddrs)),
                           ('ifa_name', ctypes.c_char_p),
                           ('ifa_flags', ctypes.c_uint),
                           ('ifa_addr', ctypes.POINTER(struct_sockaddr)),
                           ('ifa_netmask', ctypes.POINTER(struct_sockaddr)),
                           ('ifa_dstaddr', ctypes.POINTER(struct_sockaddr)),
                           ('ifa_data', ctypes.c_void_p),]

def get_broadcast_addrs():
    struct_ifaddrs_p = ctypes.POINTER(struct_ifaddrs)
    ifa = struct_ifaddrs(None)
    ifap = ctypes.cast(ctypes.addressof(ifa),
                       struct_ifaddrs_p)
    _getifaddrs(ctypes.pointer(ifap))
    ifa = ifap
    ret = []
    while ifa:
        if ifa.contents.ifa_addr.contents.sa_family == socket.AF_INET and \
           (ifa.contents.ifa_flags & 0x2) == 0x2:
            sa_in = ctypes.cast(ifa.contents.ifa_dstaddr,
                                ctypes.POINTER(struct_sockaddr_in)).contents
            ret.append(_inet_ntoa(sa_in.sin_addr.s_addr).decode('ascii'))
        ifa = ifa.contents.ifa_next
    _freeifaddrs(ifap)
    return ret

def rx_thread():
    rx = socket.socket(socket.AF_INET,
                       socket.SOCK_DGRAM)
    rx.bind((socket.gethostname(), 6666))
    while True:
        sys.stdout.write(rx.recv(1024))

def tx_thread():
    tx = socket.socket(socket.AF_INET,
                       socket.SOCK_DGRAM)
    tx.setsockopt(socket.SOL_SOCKET,
                  socket.SO_BROADCAST,
                  1)
    broadcast_addrs = get_broadcast_addrs()
    while True:
        for addr in broadcast_addrs:
            tx.sendto(sys.stdin.readline().encode('ascii'),
                      (addr, 6667))
            
t = threading.Thread(target=rx_thread, daemon=True)
t.start()
threading.Thread(target=tx_thread, daemon=True).start()
t.join()