{"action":"closed","issue":{"url":"https://api.github.com/repos/weaveworks/weave/issues/1612","labels_url":"https://api.github.com/repos/weaveworks/weave/issues/1612/labels{/name}","comments_url":"https://api.github.com/repos/weaveworks/weave/issues/1612/comments","events_url":"https://api.github.com/repos/weaveworks/weave/issues/1612/events","html_url":"https://github.com/weaveworks/weave/issues/1612","id":114162644,"number":1612,"title":"fastdp breaks if you set WEAVE_MTU too large ","user":{"login":"dpw","id":15074,"avatar_url":"https://avatars.githubusercontent.com/u/15074?v=3","gravatar_id":"","url":"https://api.github.com/users/dpw","html_url":"https://github.com/dpw","followers_url":"https://api.github.com/users/dpw/followers","following_url":"https://api.github.com/users/dpw/following{/other_user}","gists_url":"https://api.github.com/users/dpw/gists{/gist_id}","starred_url":"https://api.github.com/users/dpw/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/dpw/subscriptions","organizations_url":"https://api.github.com/users/dpw/orgs","repos_url":"https://api.github.com/users/dpw/repos","events_url":"https://api.github.com/users/dpw/events{/privacy}","received_events_url":"https://api.github.com/users/dpw/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/weaveworks/weave/labels/chore","name":"chore","color":"207de5"}],"state":"closed","locked":false,"assignee":{"login":"dpw","id":15074,"avatar_url":"https://avatars.githubusercontent.com/u/15074?v=3","gravatar_id":"","url":"https://api.github.com/users/dpw","html_url":"https://github.com/dpw","followers_url":"https://api.github.com/users/dpw/followers","following_url":"https://api.github.com/users/dpw/following{/other_user}","gists_url":"https://api.github.com/users/dpw/gists{/gist_id}","starred_url":"https://api.github.com/users/dpw/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/dpw/subscriptions","organizations_url":"https://api.github.com/users/dpw/orgs","repos_url":"https://api.github.com/users/dpw/repos","events_url":"https://api.github.com/users/dpw/events{/privacy}","received_events_url":"https://api.github.com/users/dpw/received_events","type":"User","site_admin":false},"milestone":{"url":"https://api.github.com/repos/weaveworks/weave/milestones/17","html_url":"https://github.com/weaveworks/weave/milestones/1.2.1","labels_url":"https://api.github.com/repos/weaveworks/weave/milestones/17/labels","id":1370645,"number":17,"title":"1.2.1","description":"","creator":{"login":"rade","id":109109,"avatar_url":"https://avatars.githubusercontent.com/u/109109?v=3","gravatar_id":"","url":"https://api.github.com/users/rade","html_url":"https://github.com/rade","followers_url":"https://api.github.com/users/rade/followers","following_url":"https://api.github.com/users/rade/following{/other_user}","gists_url":"https://api.github.com/users/rade/gists{/gist_id}","starred_url":"https://api.github.com/users/rade/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/rade/subscriptions","organizations_url":"https://api.github.com/users/rade/orgs","repos_url":"https://api.github.com/users/rade/repos","events_url":"https://api.github.com/users/rade/events{/privacy}","received_events_url":"https://api.github.com/users/rade/received_events","type":"User","site_admin":false},"open_issues":9,"closed_issues":8,"state":"open","created_at":"2015-10-22T15:23:27Z","updated_at":"2015-10-30T14:56:46Z","due_on":null,"closed_at":null},"comments":1,"created_at":"2015-10-29T22:42:48Z","updated_at":"2015-10-30T14:56:46Z","closed_at":"2015-10-30T14:56:46Z","body":"Where \"too large\" means somewhere around 3500 (i.e., much smaller than the 8000+ byte MTUs you want to fully exploit 9000 byte jumbo ethernet frames)\r\n\r\nThis is because go-odp allocates a 4096 byte buffer to receive netlink messages.  With a large MTU, it will receive an ODP miss message too big for the buffer, leading to an error.\r\n\r\nBut go-odp used a 4096 byte buffer from day one.  So how did the fast datapath preview manage to support larger MTUs, but 1.2.0 can't?  Because 1.2.0 attempts to verify that the MTU works over vxlan, and so promptly sends a maximum sized packet on every new connection, triggering the error.  The preview did not do that, so it would tend to set up flows based on small packets (e.g. TCP handshake packets), and MTU-sized packets would never lead to misses."}}