An old OpenBSD pf.conf circa 3.1.

pf.conf

# Basic openbsd pf.conf file circa 3.1. (would need updating to use)
#
# Required order: options, normalization, queueing, translation, filtering.
# Macros and tables may be defined and used anywhere.
# Note that translation rules are first match while filter rules are last match.

# Macros: define common values, so they can be referenced and changed easily.
ext_if="xl0"  # replace with actual external interface name i.e., dc0
external_addr="52.218.113.29"
# Internal network info if needed
#int_if="sis0"    # replace with actual internal interface name i.e., dc1
#internal_net="10.1.1.0/24"

# Tables: similar to macros, but more flexible for many addresses.
table <nonroute> { 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 127.0.0.0/8, 255.255.255.255/32 }

# read in assholes table from /etc/assholes. the perfect place for kiddiots
table <assholes> persist file "/etc/assholes" 

# Options: tune the behavior of pf, default values are given.
set timeout { interval 30, frag 10 }
set timeout { tcp.first 120, tcp.opening 30, tcp.established 86400 }
set timeout { tcp.closing 900, tcp.finwait 45, tcp.closed 90 }
set timeout { udp.first 60, udp.single 30, udp.multiple 60 }
set timeout { icmp.first 20, icmp.error 10 }
set timeout { other.first 60, other.single 30, other.multiple 60 }
set limit { states 10000, frags 5000 }
set loginterface none
set optimization normal
set block-policy drop
set require-order yes

# Normalization: reassemble fragments and resolve or reduce traffic ambiguities.
scrub in all

# Queueing: rule-based bandwidth control.
#altq on $ext_if bandwidth 2Mb cbq queue { dflt, developers, marketing }
#queue dflt bandwidth 5% cbq(default)
#queue developers bandwidth 80%
#queue marketing  bandwidth 15%
#
# From http://www.benzedrine.cx/ackpri.html
# Even when a TCP connection is used to send data only in one direction
# (like when downloading a file through ftp), TCP acknowledgements (ACKs)
# must be sent in the opposite direction, or the peer will assume that its
# packets got lost and retransmit them. To keep the peer sending data at
# the maximum rate, it's important to promptly send the ACKs back.

# When the uplink is saturated by other connections (like a concurrent
# upload), all outgoing packets get delayed equally by default. Hence, a
# concurrent upload saturating the uplink causes the outgoing ACKs for the
# download to get delayed, which causes the drop in the download
# throughput.

altq on $ext_if priq bandwidth 200Kb queue { q_pri, q_def }
queue q_pri priority 7
queue q_def priority 1 priq(default)

pass out on $ext_if proto tcp from $ext_if to any flags S/SA \
        keep state queue (q_def, q_pri)
pass in  on $ext_if proto tcp from any to $ext_if flags S/SA \
                keep state queue (q_def, q_pri)
 
pass out on $ext_if from any to any port 22 queue q_pri
pass out on $ext_if from any to any port 6667 queue q_pri


# Translation: specify how addresses are to be mapped or redirected.
# nat: packets going out through $ext_if with source address $internal_net will
# get translated as coming from the address of $ext_if, a state is created for
# such packets, and incoming packets will be redirected to the internal address.
#nat on $ext_if from $internal_net to any -> ($ext_if)

# rdr: packets coming in on $ext_if with destination $external_addr:1234 will
# be redirected to 10.1.1.1:5678. A state is created for such packets, and
# outgoing packets will be translated as coming from the external address.
#rdr on $ext_if proto tcp from any to $external_addr/32 port 1234 -> 10.1.1.1 port 5678

# rdr outgoing FTP requests to the ftp-proxy
#rdr on $int_if proto tcp from any to any port ftp -> 127.0.0.1 port 8021

# spamd-setup puts addresses to be redirected into table <spamd>.
#table <spamd> persist
#no rdr on { lo0, lo1 } from any to any
#rdr inet proto tcp from <spamd> to any port smtp -> 127.0.0.1 port 8025

# Filtering: the implicit first two rules are
pass in all
pass out all

# block all incoming packets but allow ssh, pass all outgoing tcp and udp
# connections and keep state, logging blocked packets.
block return-rst log on $ext_if proto tcp from any to any
block log on $ext_if from any to any

# don't allow anyone to spoof non-routeable addresses
block in log quick on $ext_if from <nonroute> to any
block out log quick on $ext_if from any to <nonroute>

#disallow assholes
block log quick on $ext_if from <assholes> to any

# allow ftp
pass in quick on $ext_if proto { tcp, udp } from any to any port = 20  keep state
pass out quick on $ext_if proto { tcp, udp } from any to any port = 20  keep state
pass in quick on $ext_if proto { tcp, udp } from any to any port = 21  keep state
pass in quick on $ext_if proto { tcp, udp } from any to any port 60000><65535 keep state
# ssh, smtp, dns, and ident...
pass in quick on $ext_if proto { tcp, udp } from any to any port = 22  keep state
pass in quick on $ext_if proto { tcp, udp } from any to any port = 25 keep state
# alternate smtp port
pass in quick on $ext_if proto { tcp, udp } from any to any port = 2525 keep state
pass in quick on $ext_if proto { tcp, udp } from any to any port = 53 keep state
pass in quick on $ext_if proto { tcp, udp } from any to any port = 113 keep state
# allow finger, but keep track of who uses it.
pass in log quick on $ext_if proto { tcp, udp } from any to any port = 79 keep state
# allow http and https
pass in quick on $ext_if proto { tcp, udp } from any to any port = 80 keep state
pass in quick on $ext_if proto { tcp, udp } from any to any port = 443 keep state
#allow spop and imaps
pass in quick on $ext_if proto { tcp, udp } from any to any port = 993 keep state
pass in quick on $ext_if proto { tcp, udp } from any to any port = 995 keep state
# ldap and ldaps disabled for now
#pass in quick on $ext_if proto { tcp, udp } from any to any port = 389 keep state
#pass in quick on $ext_if proto { tcp, udp } from any to any port = 636 keep state
# rsync disabled for now
#pass in quick on $ext_if proto { tcp, udp } from any to any port = 873 keep state
#allow jabber and sjabber irc disabled for now
pass in quick on $ext_if proto { tcp, udp } from any to any port = 5222 keep state
pass in quick on $ext_if proto { tcp, udp } from any to any port = 5223 keep state
pass in quick on $ext_if proto udp from any to any port = 5269 keep state
pass in quick on $ext_if proto tcp from any to any port = 5269 flags S/SA keep state

#pass in quick on $ext_if proto { tcp, udp } from any to any port = 6667 keep state
pass in quick on $ext_if proto udp from any to any port = 7000 keep state

# pass out/in certain ICMP queries and keep state (ping)
# state matching is done on host addresses and ICMP id (not
# type/code), so replies (like 0/0 for 8/0) will match queries
# ICMP error messages (which always refer to a TCP/UDP
# packet) are handled by the TCP/UDP states

# icmp network unreachable
pass in  on $ext_if inet proto icmp all icmp-type 0 code 0 keep state
# icmp network unreachable
pass in  quick on $ext_if inet proto icmp all icmp-type 3 code 0 keep state
# icmp echo request
pass in  quick on $ext_if inet proto icmp all icmp-type 8 code 0 keep state
# icmp TTL = 0 (for traceroutes)
pass in  quick on $ext_if inet proto icmp all icmp-type 11 code 0 keep state
# allow all icmp out by default
pass out quick on $ext_if inet proto icmp all keep state

# pass incoming packets destined to the addresses given in table <foo>.
# pass in on $ext_if proto { tcp, udp } from any to <foo> port 80 keep state


# and let out-going traffic out and maintain state on established connections
# -- The flags S on the keep state is to ensure that state tracking starts
#    only on the first outbound packet in a tcp session.
#    unnecessary consumption of state table entries.
# -- The flag s only works on the tcp protocol, so three entries are required 
#    to cover all three protocols (tcp, udp, icmp).

pass out quick on $ext_if proto tcp all flags S/SA keep state
pass out quick on $ext_if proto udp all keep state


# let everything out to everywhere
pass  out quick on $ext_if proto { tcp, udp } all keep state
pass  out on $ext_if all 

# pass incoming ports for ftp-proxy
#pass in on $ext_if inet proto tcp from any to $ext_if user proxy keep state

# assign packets to a queue.
#pass out on $ext_if from 192.168.0.0/24 to any keep state queue developers
#pass out on $ext_if from 192.168.1.0/24 to any keep state queue marketing