Dead Packets

30/11/2011

Configurando o OpenVPN

Filed under: vpn — drak @ 10:25 PM

Segue abaixo um guia para instalação do OpenVPN para prover acesso remoto via VPN client-to-site, agradeço ao comedor voraz de picanha que me deu de bandeja esse tutorial.

Instalar o OpenVPN versão 2.2.0 ou superior pois tem melhores recursos e estabilidade;
Após instalação, copiar a pasta /usr/share/doc/openvpn-2.2.0/easy-rsa/2.0 para /etc/openvpn/easy-rsa
Editar os campos do arquivo /etc/openvpn/easy-rsa/vars

export KEY_COUNTRY="BR"
export KEY_PROVINCE="SP"
export KEY_CITY="CIDADE"
export KEY_ORG="ORGANIZACAO"
export KEY_EMAIL="root@localhost"

Na pasta /etc/openvpn/easy-rsa digitar os comandos:

source ./vars # Executa arquivo vars
./clean-all # Limpa todas as chaves
./pkitool --initca => # Cria CA
./pkitool --server server => # Cria certificado do servidor
cd keys
cp server.crt server.key ca.crt dh1024.pem ../../

5) Para criar o certificado para os clientes, use os comandos:

cd /etc/openvpn/easy-rsa
source ./vars
./build-key nome_do_usuario

Responda todas as perguntas e coloque uma senha

Configure o arquivo /etc/openvpn/server.conf, exemplo abaixo:

#################################################
# Sample OpenVPN 2.0 config file for            #
# multi-client server.                          #
#               				#
# This file is for the server side              #
# of a many-clients  one-server              #
# OpenVPN configuration.                        #
#               				#
# OpenVPN also supports                         #
# single-machine  single-machine             #
# configurations (See the Examples page         #
# on the web site for more info).               #
#               				#
# This config should work on Windows            #
# or Linux/BSD systems.  Remember on            #
# Windows to quote pathnames and use            #
# double backslashes, e.g.:                     #
# "C:\\Program Files\\OpenVPN\\config\\foo.key" #
#               				#
# Comments are preceded with '#' or ';'         #
#################################################

# Which local IP address should OpenVPN
# listen on? (optional)
;local a.b.c.d

# Which TCP/UDP port should OpenVPN listen on?
# If you want to run multiple OpenVPN instances
# on the same machine, use a different port
# number for each one.  You will need to
# open up this port on your firewall.
port 1194

# TCP or UDP server?
proto tcp
;proto udp

# "dev tun" will create a routed IP tunnel,
# "dev tap" will create an ethernet tunnel.
# Use "dev tap0" if you are ethernet bridging
# and have precreated a tap0 virtual interface
# and bridged it with your ethernet interface.
# If you want to control access policies
# over the VPN, you must create firewall
# rules for the the TUN/TAP interface.
# On non-Windows systems, you can give
# an explicit unit number, such as tun0.
# On Windows, use "dev-node" for this.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
dev tap
;dev tun

# Windows needs the TAP-Win32 adapter name
# from the Network Connections panel if you
# have more than one.  On XP SP2 or higher,
# you may need to selectively disable the
# Windows firewall for the TAP adapter.
# Non-Windows systems usually don't need this.
;dev-node MyTap

# SSL/TLS root certificate (ca), certificate
# (cert), and private key (key).  Each client
# and the server must have their own cert and
# key file.  The server and all clients will
# use the same ca file.
#
# See the "easy-rsa" directory for a series
# of scripts for generating RSA certificates
# and private keys.  Remember to use
# a unique Common Name for the server
# and each of the client certificates.
#
# Any X509 key management system can be used.
# OpenVPN can also use a PKCS #12 formatted key file
# (see "pkcs12" directive in man page).
ca ca.crt
cert server.crt
key server.key  # This file should be kept secret

# Diffie hellman parameters.
# Generate your own with:
#   openssl dhparam -out dh1024.pem 1024
# Substitute 2048 for 1024 if you are using
# 2048 bit keys.
dh dh1024.pem

# Configure server mode and supply a VPN subnet
# for OpenVPN to draw client addresses from.
# The server will take 10.8.0.1 for itself,
# the rest will be made available to clients.
# Each client will be able to reach the server
# on 10.8.0.1. Comment this line out if you are
# ethernet bridging. See the man page for more info.
server 10.8.0.1 255.255.255.0

# Maintain a record of client  virtual IP address
# associations in this file.  If OpenVPN goes down or
# is restarted, reconnecting clients can be assigned
# the same virtual IP address from the pool that was
# previously assigned.
ifconfig-pool-persist ipp.txt

# Configure server mode for ethernet bridging.
# You must first use your OS's bridging capability
# to bridge the TAP interface with the ethernet
# NIC interface.  Then you must manually set the
# IP/netmask on the bridge interface, here we
# assume 10.8.0.4/255.255.255.0.  Finally we
# must set aside an IP range in this subnet
# (start=10.8.0.50 end=10.8.0.100) to allocate
# to connecting clients.  Leave this line commented
# out unless you are ethernet bridging.
;server-bridge 10.8.0.4 255.255.255.0 10.8.0.50 10.8.0.100

# Configure server mode for ethernet bridging
# using a DHCP-proxy, where clients talk
# to the OpenVPN server-side DHCP server
# to receive their IP address allocation
# and DNS server addresses.  You must first use
# your OS's bridging capability to bridge the TAP
# interface with the ethernet NIC interface.
# Note: this mode only works on clients (such as
# Windows), where the client-side TAP adapter is
# bound to a DHCP client.
;server-bridge

# Push routes to the client to allow it
# to reach other private subnets behind
# the server.  Remember that these
# private subnets will also need
# to know to route the OpenVPN client
# address pool (10.8.0.0/255.255.255.0)
# back to the OpenVPN server.
push "route 192.168.0.0 255.255.0.0"

# To assign specific IP addresses to specific
# clients or if a connecting client has a private
# subnet behind it that should also have VPN access,
# use the subdirectory "ccd" for client-specific
# configuration files (see man page for more info).

# EXAMPLE: Suppose the client
# having the certificate common name "Thelonious"
# also has a small subnet behind his connecting
# machine, such as 192.168.40.128/255.255.255.248.
# First, uncomment out these lines:
;client-config-dir ccd
;route 192.168.40.128 255.255.255.248
# Then create a file ccd/Thelonious with this line:
#   iroute 192.168.40.128 255.255.255.248
# This will allow Thelonious' private subnet to
# access the VPN.  This example will only work
# if you are routing, not bridging, i.e. you are
# using "dev tun" and "server" directives.

# EXAMPLE: Suppose you want to give
# Thelonious a fixed VPN IP address of 10.9.0.1.
# First uncomment out these lines:
;client-config-dir ccd
;route 10.9.0.0 255.255.255.252
# Then add this line to ccd/Thelonious:
#   ifconfig-push 10.9.0.1 10.9.0.2

# Suppose that you want to enable different
# firewall access policies for different groups
# of clients.  There are two methods:
# (1) Run multiple OpenVPN daemons, one for each
#     group, and firewall the TUN/TAP interface
#     for each group/daemon appropriately.
# (2) (Advanced) Create a script to dynamically
#     modify the firewall in response to access
#     from different clients.  See man
#     page for more info on learn-address script.
;learn-address ./script

# If enabled, this directive will configure
# all clients to redirect their default
# network gateway through the VPN, causing
# all IP traffic such as web browsing and
# and DNS lookups to go through the VPN
# (The OpenVPN server machine may need to NAT
# or bridge the TUN/TAP interface to the internet
# in order for this to work properly).
;push "redirect-gateway def1 bypass-dhcp"

# Certain Windows-specific network settings
# can be pushed to clients, such as DNS
# or WINS server addresses.  CAVEAT:
# http://openvpn.net/faq.html#dhcpcaveats
# The addresses below refer to the public
# DNS servers provided by opendns.com.
;push "dhcp-option DNS 208.67.222.222"
;push "dhcp-option DNS 208.67.220.220"

# Uncomment this directive to allow different
# clients to be able to "see" each other.
# By default, clients will only see the server.
# To force clients to only see the server, you
# will also need to appropriately firewall the
# server's TUN/TAP interface.
;client-to-client

# Uncomment this directive if multiple clients
# might connect with the same certificate/key
# files or common names.  This is recommended
# only for testing purposes.  For production use,
# each client should have its own certificate/key
# pair.
#
# IF YOU HAVE NOT GENERATED INDIVIDUAL
# CERTIFICATE/KEY PAIRS FOR EACH CLIENT,
# EACH HAVING ITS OWN UNIQUE "COMMON NAME",
# UNCOMMENT THIS LINE OUT.
;duplicate-cn

# The keepalive directive causes ping-like
# messages to be sent back and forth over
# the link so that each side knows when
# the other side has gone down.
# Ping every 10 seconds, assume that remote
# peer is down if no ping received during
# a 120 second time period.
keepalive 10 120

# For extra security beyond that provided
# by SSL/TLS, create an "HMAC firewall"
# to help block DoS attacks and UDP port flooding.
#
# Generate with:
#   openvpn --genkey --secret ta.key
#
# The server and each client must have
# a copy of this key.
# The second parameter should be '0'
# on the server and '1' on the clients.
;tls-auth ta.key 0 # This file is secret

# Select a cryptographic cipher.
# This config item must be copied to
# the client config file as well.
;cipher BF-CBC        # Blowfish (default)
;cipher AES-128-CBC   # AES
;cipher DES-EDE3-CBC  # Triple-DES

# Enable compression on the VPN link.
# If you enable it here, you must also
# enable it in the client config file.
comp-lzo

# The maximum number of concurrently connected
# clients we want to allow.
;max-clients 100

# It's a good idea to reduce the OpenVPN
# daemon's privileges after initialization.
#
# You can uncomment this out on
# non-Windows systems.
;user nobody
;group nobody

# The persist options will try to avoid
# accessing certain resources on restart
# that may no longer be accessible because
# of the privilege downgrade.
persist-key
persist-tun

# Output a short status file showing
# current connections, truncated
# and rewritten every minute.
status openvpn-status.log

# By default, log messages will go to the syslog (or
# on Windows, if running as a service, they will go to
# the "\Program Files\OpenVPN\log" directory).
# Use log or log-append to override this default.
# "log" will truncate the log file on OpenVPN startup,
# while "log-append" will append to it.  Use one
# or the other (but not both).
;log         openvpn.log
;log-append  openvpn.log

# Set the appropriate level of log
# file verbosity.
#
# 0 is silent, except for fatal errors
# 4 is reasonable for general usage
# 5 and 6 can help to debug connection problems
# 9 is extremely verbose
verb 3

# Silence repeating messages.  At most 20
# sequential messages of the same message
# category will be output to the log.
;mute 20

Suba o serviço de OpenVPN no servidor:

service openvpn start

Configure um cliente:
Instale o software openvpn (http://swupdate.openvpn.org/community/releases/openvpn-2.2.1-install.exe)
Copie os arquivos ca.crt, .crt e .key para a pasta config dentro da instalação do OpenVPN.
Crie o arquivo de configuração server.ovpn com o conteúdo:

client
dev tap
route-method exe
route-delay 2
proto tcp
remote 1194
resolv-retry infinite
nobind
persist-key
persist-tun
ca ca.crt
cert nome_do_usuario.crt
key nome_do_usuario.key
comp-lzo
verb 3

Inicie o serviço do OpenVPN no icone que aparecerá ao lado do relógio em seu desktop.

Como referência segue como deve ser um log de conexão feita com sucesso tanto do lado do servidor quanto do cliente:


# SERVER SIDE LOGS (/var/log/messages)
Nov 10 19:56:28 linux_server openvpn[31445]: MULTI: multi_create_instance called
Nov 10 19:56:28 linux_server openvpn[31445]: Re-using SSL/TLS context
Nov 10 19:56:28 linux_server openvpn[31445]: LZO compression initialized
Nov 10 19:56:28 linux_server openvpn[31445]: Control Channel MTU parms [ L:1576 D:140 EF:40 EB:0 ET:0 EL:0 ]
Nov 10 19:56:28 linux_server openvpn[31445]: Data Channel MTU parms [ L:1576 D:1450 EF:44 EB:135 ET:32 EL:0 AF:3/1 ]
Nov 10 19:56:28 linux_server openvpn[31445]: Local Options hash (VER=V4): '3e6d1056'
Nov 10 19:56:28 linux_server openvpn[31445]: Expected Remote Options hash (VER=V4): '31fdf004'
Nov 10 19:56:28 linux_server openvpn[31445]: TCP connection established with 192.168.1.150:12229
Nov 10 19:56:28 linux_server openvpn[31445]: TCPv4_SERVER link local: [undef]
Nov 10 19:56:28 linux_server openvpn[31445]: TCPv4_SERVER link remote: 192.168.1.150:12229
Nov 10 19:56:28 linux_server openvpn[31445]: 192.168.1.150:12229 TLS: Initial packet from 192.168.1.150:12229, sid=0c93e40e 445e3be2
Nov 10 19:56:28 linux_server openvpn[31445]: 192.168.1.150:12229 VERIFY OK: depth=1, /C=BR/ST=UF/L=Cidade/O=Organization/CN=Organization_CA/emailAddress=root@localhost
Nov 10 19:56:28 linux_server openvpn[31445]: 192.168.1.150:12229 VERIFY OK: depth=0, /C=BR/ST=UF/L=Cidade/O=Organization/CN=johndoe/emailAddress=root@localhost
Nov 10 19:56:29 linux_server openvpn[31445]: 192.168.1.150:12229 Data Channel Encrypt: Cipher 'BF-CBC' initialized with 128 bit key
Nov 10 19:56:29 linux_server openvpn[31445]: 192.168.1.150:12229 Data Channel Encrypt: Using 160 bit message hash 'SHA1' for HMAC authentication
Nov 10 19:56:29 linux_server openvpn[31445]: 192.168.1.150:12229 Data Channel Decrypt: Cipher 'BF-CBC' initialized with 128 bit key
Nov 10 19:56:29 linux_server openvpn[31445]: 192.168.1.150:12229 Data Channel Decrypt: Using 160 bit message hash 'SHA1' for HMAC authentication
Nov 10 19:56:29 linux_server openvpn[31445]: 192.168.1.150:12229 Control Channel: TLSv1, cipher TLSv1/SSLv3 DHE-RSA-AES256-SHA, 1024 bit RSA
Nov 10 19:56:29 linux_server openvpn[31445]: 192.168.1.150:12229 [johndoe] Peer Connection Initiated with 192.168.1.150:12229
Nov 10 19:56:31 linux_server openvpn[31445]: johndoe/192.168.1.150:12229 PUSH: Received control message: 'PUSH_REQUEST'
Nov 10 19:56:31 linux_server openvpn[31445]: johndoe/192.168.1.150:12229 SENT CONTROL [johndoe]: 'PUSH_REPLY,route 192.168.0.0 255.255.0.0,route-gateway 198.51.100.1,ping 10,ping-restart 120,ifconfig 198.51.100.3 255.255.255.0,push-continuation 1' (status=1)
Nov 10 19:56:31 linux_server openvpn[31445]: johndoe/192.168.1.150:12229 MULTI: Learn: 00:ff:3c:84:94:c7 -> johndoe/192.168.1.150:12229

# CLIENT SIDE LOGS (OpenVPN client logs)
Thu Nov 10 19:56:28 2011 OpenVPN 2.2.1 Win32-MSVC++ [SSL] [LZO2] built on Jul 1 2011
Thu Nov 10 19:56:28 2011 WARNING: No server certificate verification method has been enabled. See http://openvpn.net/howto.html#mitm for more info.
Thu Nov 10 19:56:28 2011 NOTE: OpenVPN 2.1 requires '--script-security 2' or higher to call user-defined scripts or executables
Thu Nov 10 19:56:28 2011 LZO compression initialized
Thu Nov 10 19:56:28 2011 Control Channel MTU parms [ L:1576 D:140 EF:40 EB:0 ET:0 EL:0 ]
Thu Nov 10 19:56:28 2011 Socket Buffers: R=[8192->8192] S=[8192->8192]
Thu Nov 10 19:56:28 2011 Data Channel MTU parms [ L:1576 D:1450 EF:44 EB:135 ET:32 EL:0 AF:3/1 ]
Thu Nov 10 19:56:28 2011 Local Options hash (VER=V4): '31fdf004'
Thu Nov 10 19:56:28 2011 Expected Remote Options hash (VER=V4): '3e6d1056'
Thu Nov 10 19:56:28 2011 Attempting to establish TCP connection with 200.10.10.10:1194
Thu Nov 10 19:56:28 2011 TCP connection established with 200.10.10.10:1194
Thu Nov 10 19:56:28 2011 TCPv4_CLIENT link local: [undef]
Thu Nov 10 19:56:28 2011 TCPv4_CLIENT link remote: 200.10.10.10:1194
Thu Nov 10 19:56:28 2011 TLS: Initial packet from 200.10.10.10:1194, sid=a2f0489d e1545cc7
Thu Nov 10 19:56:28 2011 VERIFY OK: depth=1, /C=BR/ST=UF/L=Cidade/O=Organization/CN=Organization_CA/emailAddress=root@localhost
Thu Nov 10 19:56:28 2011 VERIFY OK: depth=0, /C=BR/ST=UF/L=Cidade/O=Organization/CN=server/emailAddress=root@localhost
Thu Nov 10 19:56:29 2011 Data Channel Encrypt: Cipher 'BF-CBC' initialized with 128 bit key
Thu Nov 10 19:56:29 2011 Data Channel Encrypt: Using 160 bit message hash 'SHA1' for HMAC authentication
Thu Nov 10 19:56:29 2011 Data Channel Decrypt: Cipher 'BF-CBC' initialized with 128 bit key
Thu Nov 10 19:56:29 2011 Data Channel Decrypt: Using 160 bit message hash 'SHA1' for HMAC authentication
Thu Nov 10 19:56:29 2011 Control Channel: TLSv1, cipher TLSv1/SSLv3 DHE-RSA-AES256-SHA, 1024 bit RSA
Thu Nov 10 19:56:29 2011 [server] Peer Connection Initiated with 200.10.10.10:1194
Thu Nov 10 19:56:31 2011 SENT CONTROL [server]: 'PUSH_REQUEST' (status=1)
Thu Nov 10 19:56:31 2011 PUSH: Received control message: 'PUSH_REPLY,route 192.168.0.0 255.255.0.0,route-gateway 198.51.100.1,ping 10,ping-restart 120,ifconfig 198.51.100.3 255.255.255.0,push-continuation 1'
Thu Nov 10 19:56:31 2011 OPTIONS IMPORT: timers and/or timeouts modified
Thu Nov 10 19:56:31 2011 OPTIONS IMPORT: --ifconfig/up options modified
Thu Nov 10 19:56:31 2011 OPTIONS IMPORT: route options modified
Thu Nov 10 19:56:31 2011 OPTIONS IMPORT: route-related options modified
Thu Nov 10 19:56:31 2011 ROUTE default_gateway=172.16.0.1
Thu Nov 10 19:56:31 2011 TAP-WIN32 device [Local Area Connection 2] opened: \\.\Global\{3C8494C7-498F-46A5-8535-D2C81ABB148E}.tap
Thu Nov 10 19:56:31 2011 TAP-Win32 Driver Version 9.8
Thu Nov 10 19:56:31 2011 TAP-Win32 MTU=1500
Thu Nov 10 19:56:31 2011 Notified TAP-Win32 driver to set a DHCP IP/netmask of 198.51.100.3/255.255.255.0 on interface {3C8494C7-498F-46A5-8535-D2C81ABB148E} [DHCP-serv: 198.51.100.0, lease-time: 31536000]
Thu Nov 10 19:56:31 2011 Successful ARP Flush on interface [37] {3C8494C7-498F-46A5-8535-D2C81ABB148E}
Thu Nov 10 19:56:33 2011 TEST ROUTES: 98/98 succeeded len=98 ret=1 a=0 u/d=up
Thu Nov 10 19:56:33 2011 C:\WINDOWS\system32\route.exe ADD 192.168.0.0 MASK 255.255.0.0 198.51.100.1
OK!
Thu Nov 10 19:56:33 2011 Initialization Sequence Completed

Anúncios

02/11/2011

Troubleshooting de lentidão com firewall, MPLS e HP-UX

Filed under: checkpoint,troubleshooting — drak @ 9:20 PM

Enfrentava um problema de lentidão em um sistema web acessado por uma empresa parceira que chegava no meu cliente por uma MPLS contratada de um ISP.

Testes de ping mostravam entre 25% a 75% de perda de pacotes, a operadora já havia tentado corrigir a situação aplicando QoS no roteador de WAN mais próximo do cliente porém não surtiu efeito. No meio do caminho havia um Check Point R71.30 splat com conhecido problema de alto processamento (CPU constantemente entre 75% e 85%).

Inicialmente queria estabelecer um baseline desse sistema web que era afetado pela lentidão. Fui informado que outra empresa parceira tambem acessava esse mesmo sistema e que seu desempenho era medido por agentes que mostravam um tempo médio de resposta de 2s.

Com essa informação confrontei com o tempo a partir da parceira problemática. Eles obteram essa informação com o HttpWatch, ferramenta que provê gratuitamenta esse tipo de métrica, podemos ver um exemplo de medição para o site yahoo.com abaixo.

O tempo foi em média 30s, portanto muito maior, comparativamente, com a velocidade esperada do sistema.

O próximo passo seria um traceroute a partir da parceira afetada até o web server, não conseguimos progredir com essa abordagem pois o firewall no parceiro não possuia liberação para isso.

Mudamos a abordagem e fizemos um traceroute a partir do roteador da wan que estava na frente deste firewall (da parceira), o gateway do firewall para a rede MPLS. A partir desse ponto obtivemos o caminho até o web server, cada asterisco é um IP que mapeamos usando o traceroute.

|LAN PARCEIRA| – |FW PARC| – |ROUTER WAN PARC| – *|ROUTER1| – *|ROUTER2| – *|ROUTER WAN CUST| – *|FW CLIENTE| – *|WEB SERVER|

Com um traceroute no sentido contrário, feito a partir do firewall (pois o web server estava diretamente conectado) cruzamos as duas informações e montamos a topologia completa do ambiente afetado pelo problema:

|LAN PARCEIRA| – |FW PARC| – |ROUTER WAN PARC|* – *|ROUTER1|* – *|ROUTER2|* – *|ROUTER WAN CUST|* – *|FW CLIENTE| – *|WEB SERVER|

Com o ambiente mapeado começamos os testes. Ping a partir do equipamento ROUTER WAN PARC para o WEB SERVER indicava perdas de até 75%!

Próximo hop mesmo teste, e assim por diante, vejam os resultados.

ROUTER WAN PARC, WEB SERVER: 75%
ROUTER1, WEB SERVER: 75%
ROUTER2, WEB SERVER: 75%
ROUTER WAN CUST, WEB SERVER: 0%
FW CLIENTE: 0%

Com os resultados desses testes, imaginei que havíamos descoberto que o problema estava entre o segmento ROUTER WAN PARC e a interface mais próxima dele do ROUTER WAN CUST, porém ao fazer testes iniciando do ROUTER2 também tinhamos uma quantidade alta de perda, a príncipio eliminando a possibilidade de ser algo no segmento anteriormente suspeito.

Ao analisar o resultado das falhas de ping do ROUTER2 notamos algo estranho, ele não simplemente perdia os pacotes por time-out mas sim por algum outro motivo, vejam a imagem:

Pesquisando um pouco descobrimos que a mensagem icmp !Q era enviada quando o servidor estava com seu buffer estava cheio e não conseguia lidar com todos os pings enviados para ele, essa mensagem solicita ao host que está enviando os pacotes que o mesmo diminuia a velocidade de envio.

Outra informação importante é que, embora no firewall ele não definisse os pacotes como perdidos também estávamos recebendo pacotes de ICMP source-quench, segue um exemplo dos logs que víamos no firewall.

FIREWALL[admin]# ping -s 1400 XXX.XXX.XXX.177
PING XXX.XXX.XXX.177 (XXX.XXX.XXX.177): 1400 data bytes
1408 bytes from XXX.XXX.XXX.177: icmp_seq=0 ttl=255 time=2.025 ms
1408 bytes from XXX.XXX.XXX.177: icmp_seq=1 ttl=255 time=0.343 ms
1408 bytes from XXX.XXX.XXX.177: icmp_seq=2 ttl=255 time=0.336 ms
1408 bytes from XXX.XXX.XXX.177: icmp_seq=3 ttl=255 time=3.196 ms
...
1408 bytes from XXX.XXX.XXX.177: icmp_seq=50 ttl=255 time=0.334 ms
1408 bytes from XXX.XXX.XXX.177: icmp_seq=51 ttl=255 time=0.312 ms
1408 bytes from XXX.XXX.XXX.177: icmp_seq=52 ttl=255 time=0.672 ms
1408 bytes from XXX.XXX.XXX.177: icmp_seq=53 ttl=255 time=1.046 ms
1408 bytes from XXX.XXX.XXX.177: icmp_seq=54 ttl=255 time=0.344 ms
92 bytes from XXX.XXX.XXX.177: Source Quench
Vr HL TOS Len ID Flg off TTL Pro cks Src Dst
4 5 00 0594 00e4 0 0000 40 01 f861 XXX.XXX.XXX.10 XXX.XXX.XXX.177

1408 bytes from XXX.XXX.XXX.177: icmp_seq=55 ttl=255 time=0.456 ms
92 bytes from XXX.XXX.XXX.177: Source Quench
Vr HL TOS Len ID Flg off TTL Pro cks Src Dst
4 5 00 0594 010c 0 0000 40 01 f839 XXX.XXX.XXX.10 XXX.XXX.XXX.177

1408 bytes from XXX.XXX.XXX.177: icmp_seq=56 ttl=255 time=0.362 ms
92 bytes from XXX.XXX.XXX.177: Source Quench
Vr HL TOS Len ID Flg off TTL Pro cks Src Dst
4 5 00 0594 0132 0 0000 40 01 f813 XXX.XXX.XXX.10 XXX.XXX.XXX.177

1408 bytes from XXX.XXX.XXX.177: icmp_seq=57 ttl=255 time=0.276 ms
92 bytes from XXX.XXX.XXX.177: Source Quench
Vr HL TOS Len ID Flg off TTL Pro cks Src Dst
4 5 00 0594 0154 0 0000 40 01 f7f1 XXX.XXX.XXX.10 XXX.XXX.XXX.177

1408 bytes from XXX.XXX.XXX.177: icmp_seq=58 ttl=255 time=0.314 ms
92 bytes from XXX.XXX.XXX.177: Source Quench
Vr HL TOS Len ID Flg off TTL Pro cks Src Dst
4 5 00 0594 0178 0 0000 40 01 f7cd XXX.XXX.XXX.10 XXX.XXX.XXX.177

1408 bytes from XXX.XXX.XXX.177: icmp_seq=59 ttl=255 time=0.286 ms
92 bytes from XXX.XXX.XXX.177: Source Quench
Vr HL TOS Len ID Flg off TTL Pro cks Src Dst
4 5 00 0594 01a1 0 0000 40 01 f7a4 XXX.XXX.XXX.10 XXX.XXX.XXX.177

1408 bytes from XXX.XXX.XXX.177: icmp_seq=60 ttl=255 time=2.355 ms
92 bytes from XXX.XXX.XXX.177: Source Quench
Vr HL TOS Len ID Flg off TTL Pro cks Src Dst
4 5 00 0594 01c8 0 0000 40 01 f77d XXX.XXX.XXX.10 XXX.XXX.XXX.177

1408 bytes from XXX.XXX.XXX.177: icmp_seq=61 ttl=255 time=0.333 ms
92 bytes from XXX.XXX.XXX.177: Source Quench
Vr HL TOS Len ID Flg off TTL Pro cks Src Dst
4 5 00 0594 01ee 0 0000 40 01 f757 XXX.XXX.XXX.10 XXX.XXX.XXX.177

1408 bytes from XXX.XXX.XXX.177: icmp_seq=62 ttl=255 time=0.592 ms
92 bytes from XXX.XXX.XXX.177: Source Quench
Vr HL TOS Len ID Flg off TTL Pro cks Src Dst
4 5 00 0594 020f 0 0000 40 01 f736 XXX.XXX.XXX.10 XXX.XXX.XXX.177

Para forçar esse log a aparecer de maneira mais constante, usamos a opção de ping “flood” (ping host -f), ao fazer isso constatamos que o comportamento do servidor era o mesmo tanto para o router quanto para o firewall, que estava diretamente conectado.

Após verificação da saúde do servidor (CPU, memória, velocidade da placa de rede, erros na interface) começamos a investigar outros motivos para que essa mensagem possa ser enviada que não envolvam o servidor não estar “aguentando” a taxa de pings enviados. O servidor em questão era um HP-UX e isso nos trouxe alguns artigos interessantes.

Descobrimos que havia uma certa proteção interna nos servidores HP-UX e que havia um meio de desativar essa proteção, dada a natureza do nosso teste (envio de repetidos pings a partir de um router, que tem uma taxa de envio bem alta, certamente isso estava atrapalhando os testes. Após desabilitar a proteção seguindo o conselho de um dos blogs (Set “Source quench” to 0 as “ndd -set /dev/ip ip_send_souce_quench 0” and include this parameter inside “nddconf” file.) refizemos os testes, com os seguintes resultados:

ROUTER WAN PARC, WEB SERVER: 25%
ROUTER1, WEB SERVER: 25%
ROUTER2, WEB SERVER: 0%
ROUTER WAN CUST, WEB SERVER: 0%
FW CLIENTE: 0%

Agora sim, uma vez removido o fator “source-quench” que estava mascarando os resultados conseguimos isolar em que trecho da rede estava o real problema de lentidão. O ISP investigou o problema e informou que o problema estava com uma política de QoS nesse trecho, uma vez removida a política as perdas pararam e o acesso Web voltou ao patamar esperado (cerca de 2s).

Referências
Understanding the Ping and Traceroute Commands
HttpWatch
ICMP Source Quench
HP-UX ping source quench

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