bug: luasocket2.0.2 udp socket is trashed when setsockname fails

[Sam Roberts <vieuxtech@...>]

On bind() failure with a udp socket (:setsockname()), the descriptor
appears to be closed and set to -1.

Sorry, no time to provide a patch right now (or test with tcp), we are
attempting year end releases.

Output:

% lua bind.lua
version:        LuaSocket 2.0.2
fd:     4
setsockname:(busy)      nil     address already in use
getsockname:    nil     getsockname failed
setsockname:(free)      nil     Bad file descriptor
getsockname:    nil     getsockname failed


Replication:

-- bind.lua
require"socket"

print("version:", socket._VERSION)

u0 = socket.udp()
assert(u0:setsockname("*", 33000))

u1 = socket.udp()
print("fd:", u1:getfd())
print("setsockname:(busy)", u1:setsockname("*", 33000))
print("getsockname:", u1:getsockname())
print("setsockname:(free)", u1:setsockname("*", 33001))
print("getsockname:", u1:getsockname())

u1:close()

while true do end

os.exit(0)


System trace output:

% strace -v -e trace=network,close,shutdown lua bind.lua
[...]
version:        LuaSocket 2.0.2
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
bind(3, {sa_family=AF_INET, sin_port=htons(33000),
sin_addr=inet_addr("0.0.0.0")}, 16) = 0
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 4
fd:     4
bind(4, {sa_family=AF_INET, sin_port=htons(33000),
sin_addr=inet_addr("0.0.0.0")}, 16) = -1 EADDRINUSE (Address already
in use)
close(4)                                = 0
setsockname:(busy)      nil     address already in use
getsockname(4294967295, 0x7fff878afac0, [27906859243405328]) = -1
EBADF (Bad file descriptor)
getsockname:    nil     getsockname failed
bind(4294967295, {sa_family=AF_INET, sin_port=htons(33001),
sin_addr=inet_addr("0.0.0.0")}, 16) = -1 EBADF (Bad file descriptor)
setsockname:(free)      nil     Bad file descriptor
getsockname(4294967295, 0x7fff878afac0, [27907099761573904]) = -1
EBADF (Bad file descriptor)
getsockname:    nil     getsockname failed