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https://issues.apache.org/jira/browse/HADOOP-15250?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16373043#comment-16373043
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Steve Loughran commented on HADOOP-15250:
-----------------------------------------

bq. These parameters the two DNS ones would never work in a splitview DNS 
environment with DNS servers correctly configured to determine the hostsname. 
Remember in our scenerio we want all local traffic to the cluster to use the 
cluster network and anything destined to the datacenter networks to use the 
server interfaces. This means you should NOT be binding to a non-routable 
address. 

I guess what we are looking at is that specific situation of "bind to all nics, 
rather than just the specific one whose IP address matches what an nslookup of 
your hostname says it is bonded to". That is different, AFAIK the multihome 
stuff in there right now, which supports multihomed servers but only brings up 
the cluster on one of the set of interfaces

I think I see the problem now, but like I said, I'm not the one to be reviewing 
changes to Client. I'm also wondering if this situation is replicated 
elsewhere. Specifically, if you want HDFS to be remotely visible, then the DN 
block services need to be exported on both interfaces, YARN apps, etc, etc. If 
so, you don't want whatever fixes are needed to go into IPC Client; doing it in 
netutil would be the place for broader adoption.

bq. This also raises the question that anyone putting in values to /etc/hosts 
would cause that to bind incorrectly say like 127.0.0.10. 

An [eternal problem|https://wiki.apache.org/hadoop/ConnectionRefused], 
especially on Ubuntu.

> Split-DNS MultiHomed Server Network Cluster Network IPC Client Bind Addr Wrong
> ------------------------------------------------------------------------------
>
>                 Key: HADOOP-15250
>                 URL: https://issues.apache.org/jira/browse/HADOOP-15250
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: ipc, net
>    Affects Versions: 2.7.3, 2.9.0, 3.0.0
>         Environment: Multihome cluster with split DNS and rDNS lookup of 
> localhost returning non-routable IPAddr
>            Reporter: Greg Senia
>            Priority: Critical
>         Attachments: HADOOP-15250.patch
>
>
> We run our Hadoop clusters with two networks attached to each node. These 
> network are as follows a server network that is firewalled with firewalld 
> allowing inbound traffic: only SSH and things like Knox and Hiveserver2 and 
> the HTTP YARN RM/ATS and MR History Server. The second network is the cluster 
> network on the second network interface this uses Jumbo frames and is open no 
> restrictions and allows all cluster traffic to flow between nodes. 
>  
> To resolve DNS within the Hadoop Cluster we use DNS Views via BIND so if the 
> traffic is originating from nodes with cluster networks we return the 
> internal DNS record for the nodes. This all works fine with all the 
> multi-homing features added to Hadoop 2.x
>  Some logic around views:
> a. The internal view is used by cluster machines when performing lookups. So 
> hosts on the cluster network should get answers from the internal view in DNS
> b. The external view is used by non-local-cluster machines when performing 
> lookups. So hosts not on the cluster network should get answers from the 
> external view in DNS
>  
> So this brings me to our problem. We created some firewall rules to allow 
> inbound traffic from each clusters server network to allow distcp to occur. 
> But we noticed a problem almost immediately that when YARN attempted to talk 
> to the Remote Cluster it was binding outgoing traffic to the cluster network 
> interface which IS NOT routable. So after researching the code we noticed the 
> following in NetUtils.java and Client.java 
> Basically in Client.java it looks as if it takes whatever the hostname is and 
> attempts to bind to whatever the hostname is resolved to. This is not valid 
> in a multi-homed network with one routable interface and one non routable 
> interface. After reading through the java.net.Socket documentation it is 
> valid to perform socket.bind(null) which will allow the OS routing table and 
> DNS to send the traffic to the correct interface. I will also attach the 
> nework traces and a test patch for 2.7.x and 3.x code base. I have this test 
> fix below in my Hadoop Test Cluster.
> Client.java:
>       
> |/*|
> | | * Bind the socket to the host specified in the principal name of the|
> | | * client, to ensure Server matching address of the client connection|
> | | * to host name in principal passed.|
> | | */|
> | |InetSocketAddress bindAddr = null;|
> | |if (ticket != null && ticket.hasKerberosCredentials()) {|
> | |KerberosInfo krbInfo =|
> | |remoteId.getProtocol().getAnnotation(KerberosInfo.class);|
> | |if (krbInfo != null) {|
> | |String principal = ticket.getUserName();|
> | |String host = SecurityUtil.getHostFromPrincipal(principal);|
> | |// If host name is a valid local address then bind socket to it|
> | |{color:#FF0000}*InetAddress localAddr = 
> NetUtils.getLocalInetAddress(host);*{color}|
> |{color:#FF0000} ** {color}|if (localAddr != null) {|
> | |this.socket.setReuseAddress(true);|
> | |if (LOG.isDebugEnabled()) {|
> | |LOG.debug("Binding " + principal + " to " + localAddr);|
> | |}|
> | |*{color:#FF0000}bindAddr = new InetSocketAddress(localAddr, 0);{color}*|
> | *{color:#FF0000}{color}* |*{color:#FF0000}}{color}*|
> | |}|
> | |}|
>  
> So in my Hadoop 2.7.x Cluster I made the following changes and traffic flows 
> correctly out the correct interfaces:
>  
> diff --git 
> a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeys.java
>  
> b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeys.java
> index e1be271..c5b4a42 100644
> --- 
> a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeys.java
> +++ 
> b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeys.java
> @@ -305,6 +305,9 @@
>    public static final String  IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_KEY 
> = "ipc.client.fallback-to-simple-auth-allowed";
>    public static final boolean 
> IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_DEFAULT = false;
>  
> +  public static final String  IPC_CLIENT_NO_BIND_LOCAL_ADDR_KEY = 
> "ipc.client.nobind.local.addr";
> +  public static final boolean IPC_CLIENT_NO_BIND_LOCAL_ADDR_DEFAULT = false;
> +
>    public static final String IPC_CLIENT_CONNECT_MAX_RETRIES_ON_SASL_KEY =
>      "ipc.client.connect.max.retries.on.sasl";
>    public static final int    IPC_CLIENT_CONNECT_MAX_RETRIES_ON_SASL_DEFAULT 
> = 5;
> diff --git 
> a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java
>  
> b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java
> index a6f4eb6..7bfddb7 100644
> --- 
> a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java
> +++ 
> b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java
> @@ -129,7 +129,9 @@ public static void setCallIdAndRetryCount(int cid, int 
> rc) {
>  
>    private final int connectionTimeout;
>  
> +
>    private final boolean fallbackAllowed;
> +  private final boolean noBindLocalAddr;
>    private final byte[] clientId;
>    
>    final static int CONNECTION_CONTEXT_CALL_ID = -3;
> @@ -642,7 +644,11 @@ private synchronized void setupConnection() throws 
> IOException {
>                InetAddress localAddr = NetUtils.getLocalInetAddress(host);
>                if (localAddr != null) {
>                  this.socket.setReuseAddress(true);
> -                this.socket.bind(new InetSocketAddress(localAddr, 0));
> +                if (noBindLocalAddr) {
> +                  this.socket.bind(null);
> + } else {
> +                  this.socket.bind(new InetSocketAddress(localAddr, 0));
> +                }
>                }
>              }
>            }



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