What are the available Unix Socket types in Ruby (on Linux)?

output.txt

best	[:SOCK_STREAM, :SOCK_DGRAM, :SOCK_SEQPACKET]
:SOCK_STREAM	TYPE SOCK_STREAM
:SOCK_DGRAM	TYPE SOCK_DGRAM
:SOCK_SEQPACKET	TYPE SOCK_SEQPACKET

other	[nil, :SOCK_RAW]
nil	TYPE SOCK_STREAM
:SOCK_RAW	TYPE SOCK_DGRAM

unsupported	[:SOCK_RDM, :SOCK_PACKET, :SOCK_NONBLOCK, :SOCK_CLOEXEC]
:SOCK_RDM	Errno::ESOCKTNOSUPPORT
:SOCK_PACKET	Errno::ESOCKTNOSUPPORT
:SOCK_NONBLOCK	Errno::ESOCKTNOSUPPORT
:SOCK_CLOEXEC	Errno::ESOCKTNOSUPPORT

invalid	[:RAW_SOCK]
:RAW_SOCK	SocketError

1	DEBUG 0
2	REUSEADDR 0
3	TYPE SOCK_STREAM
4	ERROR Success (0)
5	DONTROUTE 0
6	BROADCAST 0
7	SNDBUF 212992
8	RCVBUF 212992
9	KEEPALIVE 0
10	OOBINLINE 0
11	NO_CHECK "\x00\x00\x00\x00"
12	PRIORITY "\x00\x00\x00\x00"
13	LINGER off 0sec
14	optname:14 "\x00\x00\x00\x00"
15	REUSEPORT "\x00\x00\x00\x00"
16	PASSCRED "\x00\x00\x00\x00"
17	PEERCRED pid=143083 euid=1000 egid=100 (ucred)
18	RCVLOWAT 1
19	SNDLOWAT 1
20	RCVTIMEO 0.000000sec
21	SNDTIMEO 0.000000sec
25	BINDTODEVICE ""
26	ATTACH_FILTER ""
29	TIMESTAMP "\x00\x00\x00\x00"
30	ACCEPTCONN 0
31	PEERSEC "kernel\x00"
34	PASSSEC "\x00\x00\x00\x00"
35	TIMESTAMPNS "\x00\x00\x00\x00"
36	MARK "\x00\x00\x00\x00"
37	TIMESTAMPING "\x00\x00\x00\x00\x00\x00\x00\x00"
38	PROTOCOL "\x00\x00\x00\x00"
39	DOMAIN "\x01\x00\x00\x00"
40	RXQ_OVFL "\x00\x00\x00\x00"
41	WIFI_STATUS "\x00\x00\x00\x00"
42	PEEK_OFF "\xFF\xFF\xFF\xFF"
43	NOFCS "\x00\x00\x00\x00"
44	LOCK_FILTER "\x00\x00\x00\x00"
45	SELECT_ERR_QUEUE "\x00\x00\x00\x00"
46	BUSY_POLL "\x00\x00\x00\x00"
47	MAX_PACING_RATE "\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF"
48	BPF_EXTENSIONS "@\x00\x00\x00"
49	optname:49 "\xFF\xFF\xFF\xFF"
55	optname:55 "\x00\x00\x00\x00\x00@\x03\x00\x00\x00\x00\x00\x00@\x03\x00\x00\x00\x00\x00\x00\x00\x00
56	optname:56 "\x00\x00\x00\x00"
57	optname:57 "2\x10\x00\x00\x00\x00\x00\x00"
59	optname:59 "\x01\x00\x00\x00d\x00\x00\x00\xE3\x03\x00\x00"
60	optname:60 "\x00\x00\x00\x00"
61	optname:61 "\x00\x00\x00\x00\x00\x00\x00\x00"
62	optname:62 "\x00\x00\x00\x00"
63	optname:63 "\x00\x00\x00\x00"
64	optname:64 "\x00\x00\x00\x00"
66	optname:66 "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
67	optname:67 "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
69	optname:69 "\x00\x00\x00\x00"
72	optname:72 "\x00\x00\x00\x00"

check DGRAM sockopts against RAW sockopts
value mismatch: [57]: "optname:57 \"3\\x10\\x00\\x00\\x00\\x00\\x00\\x00\"" "optname:57 \"5\\x10\\x00\\x00\\x00\\x00\\x00\\x00\""
DONE

unix_sockets.rb

# NOTE: these are _Unix_ sockets, not network sockets

require 'socket'

# get the level 1 socket option for num
def get_opt sock, num
  sock.getsockopt(1, num)
end

# a short readable string version of the socket option
def string_opt sock, num
  get_opt(sock, num).inspect[30, 99].chop
end

# get the socket type, option number 3
def get_type sock
  string_opt sock, Socket::SO_TYPE # 3
end

# return an array of strings
def brute_sockopts sock
  ary = []
  99.times { |i|
    begin
      str = string_opt(sock, i)
    rescue Errno::ENOPROTOOPT, Errno::EINVAL
      next
    end
    ary[i] = str
  }
  ary
end

# man page for unix sockets:
# SOCK_STREAM, SOCK_DGRAM, SOCK_SEQPACKET
# let's try:

socktypes = {
  best: [:SOCK_STREAM, :SOCK_DGRAM, :SOCK_SEQPACKET],
  other: [nil, :SOCK_RAW],
  unsupported: [:SOCK_RDM, :SOCK_PACKET, :SOCK_NONBLOCK, :SOCK_CLOEXEC],
  invalid: [:RAW_SOCK],
}

socktypes.each { |group, types|
  puts [group, types.inspect].join("\t")
  types.each { |type|
    if type.nil?
      a, b = UNIXSocket.pair
    else
      begin
        a, b = UNIXSocket.pair(type)
      rescue StandardError => e
        puts [type.inspect, e.class].join("\t")
        next
      end
    end
    puts [type.inspect, get_type(a)].join("\t")
    a.close; b.close
  }
  puts
}

sock_stream, other_stream = UNIXSocket.pair(:SOCK_STREAM)
other_stream.close
opts_stream = brute_sockopts(sock_stream)
puts opts_stream.map.with_index { |val, idx|
  val and [idx, val].join("\t")
}.compact.join("\n")

sock_dgram, other_dgram = UNIXSocket.pair(:DGRAM)
other_dgram.close
opts_dgram = brute_sockopts(sock_dgram)

sock_nil, other_nil = UNIXSocket.pair
other_nil.close
opts_nil = brute_sockopts(sock_nil)

sock_raw, other_raw = UNIXSocket.pair(:RAW)
other_raw.close
opts_raw = brute_sockopts(sock_raw)

puts
puts "check DGRAM sockopts against RAW sockopts"
opts_dgram.each.with_index { |val, idx|
  other = opts_raw[idx]
  if val.class != other.class
    puts format("class mismatch: [%i]: %s %s", idx, val.class, other.class)
  end

  if val != other
    puts format("value mismatch: [%i]: %s %s", idx, val.inspect, other.inspect)
  end
}

puts "DONE"