Date: Thu, 03 May 2001 10:12:27 -0700 From: Lars Eggert <larse@ISI.EDU> To: "Louis A. Mamakos" <louie@TransSys.COM> Cc: Erik Salander <erik@whistle.com>, freebsd-net@FreeBSD.ORG Subject: Re: gifs and tcpdump Message-ID: <3AF1917B.2AC0E900@isi.edu> References: <3AF0B57B.4D789393@whistle.com> <200105031311.f43DB9711069@whizzo.transsys.com>
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This is a cryptographically signed message in MIME format. --------------msEC7F884CEF164907A5775908 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit "Louis A. Mamakos" wrote: > > Should I be able to "tcpdump -i gif0"? tcpdump indicates it's listening > > on gif0 but I never capture anything. Yes, you should. If you send traffic over it, but from what Louis wrote, maybe you don't. > Traffic going over an ESP tunnel never actual transits the tunnel > interface. In fact, if you arrange to have the right routes installed, > you don't even need the gif interface at all. From some recent experiments > I've done, the gif interface seems to be used only for: > > - side effect of installed host routes which are needed when > matching the IPSEC policy specification > > - carrying traffic that isn't matching the IPSEC policy specification > (if there is any at all) Gif interfaces are for IPIP tunnels. Using them in parallel with IPsec tunnels to trick routing into sending traffic over an SA is a bad hack IMHO. Also, depending on the order you set up tunnels and SAs, you may see strange effects. > I found this very counter intuitive; however, if you do a tcpdump on the > physical interface carrying the tunnel traffic, you'll see that the IPSEC > traffic isn't in an ipip encapsulation at all. Exactly, it is "IPsec tunnel mode" (type 50 or 51 packet with a type 4 packet inside), which is different from IPIP (type 4 packet with a type 4 packet inside). > Yes, I found this very counter-intuititve. From what I can tell, there's > no easy way to do a tcpdump and see the unencrypted traffic as it exits > the IPSEC tunnel. What I may try next is to specify a transport-mode > IPSEC policy that covers the gif interface tunnel endpoints, but I don't > know if that wll work or not. It works, and makes routing much cleaner, since now the tunnel devices represented in the routing table are the ones that actually carry the traffic. There's an ID that has more information on this: ftp://ftp.isi.edu/internet-drafts/draft-touch-ipsec-vpn-01.txt Lars -- Lars Eggert <larse@isi.edu> Information Sciences Institute http://www.isi.edu/larse/ University of Southern California --------------msEC7F884CEF164907A5775908 Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIIIIwYJKoZIhvcNAQcCoIIIFDCCCBACAQExCzAJBgUrDgMCGgUAMAsGCSqGSIb3DQEHAaCC BfQwggLYMIICQaADAgECAgMDIwUwDQYJKoZIhvcNAQEEBQAwgZQxCzAJBgNVBAYTAlpBMRUw EwYDVQQIEwxXZXN0ZXJuIENhcGUxFDASBgNVBAcTC0R1cmJhbnZpbGxlMQ8wDQYDVQQKEwZU aGF3dGUxHTAbBgNVBAsTFENlcnRpZmljYXRlIFNlcnZpY2VzMSgwJgYDVQQDEx9QZXJzb25h bCBGcmVlbWFpbCBSU0EgMTk5OS45LjE2MB4XDTAwMDgyNDIwMzAwOFoXDTAxMDgyNDIwMzAw OFowVDEPMA0GA1UEBBMGRWdnZXJ0MQ0wCwYDVQQqEwRMYXJzMRQwEgYDVQQDEwtMYXJzIEVn Z2VydDEcMBoGCSqGSIb3DQEJARYNbGFyc2VAaXNpLmVkdTCBnzANBgkqhkiG9w0BAQEFAAOB jQAwgYkCgYEAz1yfcNs53rvhuw8gSDvr2+/snP8GduYY7x7WkJdyvcwb4oipNpWYIkMGP214 Zv1KrgvntGaG+jeugAGQt0n64VusgcIzQ6QDRtnMgdQDTAkVSQ2eLRSQka+nAPx6SFKJg79W EEHmgKQBMtZdMBYtYv/mTOcpm7jTJVg+7W6n04UCAwEAAaN3MHUwKgYFK2UBBAEEITAfAgEA MBowGAIBBAQTTDJ1TXlmZkJOVWJOSkpjZFoyczAYBgNVHREEETAPgQ1sYXJzZUBpc2kuZWR1 MAwGA1UdEwEB/wQCMAAwHwYDVR0jBBgwFoAUiKvxYINmVfTkWMdGHcBhvSPXw4wwDQYJKoZI hvcNAQEEBQADgYEAi65fM/jSCaPhRoA9JW5X2FktSFhE5zkIpFVPpv33GWPPNrncsK13HfZm s0B1rNy2vU7UhFI/vsJQgBJyffkLFgMCjp3uRZvBBjGD1q4yjDO5yfMMjquqBpZtRp5op3lT d01faA58ZCB5sxCb0ORSxvXR8tc9DJO0JIpQILa6vIAwggMUMIICfaADAgECAgELMA0GCSqG SIb3DQEBBAUAMIHRMQswCQYDVQQGEwJaQTEVMBMGA1UECBMMV2VzdGVybiBDYXBlMRIwEAYD VQQHEwlDYXBlIFRvd24xGjAYBgNVBAoTEVRoYXd0ZSBDb25zdWx0aW5nMSgwJgYDVQQLEx9D ZXJ0aWZpY2F0aW9uIFNlcnZpY2VzIERpdmlzaW9uMSQwIgYDVQQDExtUaGF3dGUgUGVyc29u YWwgRnJlZW1haWwgQ0ExKzApBgkqhkiG9w0BCQEWHHBlcnNvbmFsLWZyZWVtYWlsQHRoYXd0 ZS5jb20wHhcNOTkwOTE2MTQwMTQwWhcNMDEwOTE1MTQwMTQwWjCBlDELMAkGA1UEBhMCWkEx FTATBgNVBAgTDFdlc3Rlcm4gQ2FwZTEUMBIGA1UEBxMLRHVyYmFudmlsbGUxDzANBgNVBAoT BlRoYXd0ZTEdMBsGA1UECxMUQ2VydGlmaWNhdGUgU2VydmljZXMxKDAmBgNVBAMTH1BlcnNv bmFsIEZyZWVtYWlsIFJTQSAxOTk5LjkuMTYwgZ8wDQYJKoZIhvcNAQEBBQADgY0AMIGJAoGB ALNpWpfU0BYLerXFXekhnCNyzRJMS/d+z8f7ynIk9EJSrFeV43theheE5/1yOTiUtOrtZaeS Bl694GX2GbuUeXZMPrlocHWEHPQRdAC8BSxPCQMXMcz0QdRyxqZd4ohEsIsuxE3x8NaFPmzz lZR4kX5A6ZzRjRVXjsJz5TDeRvVPAgMBAAGjNzA1MBIGA1UdEwEB/wQIMAYBAf8CAQAwHwYD VR0jBBgwFoAUcknCczTGVfQLdnKBfnf0h+fGsg4wDQYJKoZIhvcNAQEEBQADgYEAa8ZZ6TH6 6bbssQPY33Jy/pFgSOrGVd178GeOxmFw523CpTfYnbcXKFYFi91cdW/GkZDGbGZxE9AQfGuR b4bgITYtwdfqsgmtzy1txoNSm/u7/pyHnfy36XSS5FyXrvx+rMoNb3J6Zyxrc/WG+Z31AG70 HQfOnZ6CYynvkwl+Vd4xggH3MIIB8wIBATCBnDCBlDELMAkGA1UEBhMCWkExFTATBgNVBAgT DFdlc3Rlcm4gQ2FwZTEUMBIGA1UEBxMLRHVyYmFudmlsbGUxDzANBgNVBAoTBlRoYXd0ZTEd MBsGA1UECxMUQ2VydGlmaWNhdGUgU2VydmljZXMxKDAmBgNVBAMTH1BlcnNvbmFsIEZyZWVt YWlsIFJTQSAxOTk5LjkuMTYCAwMjBTAJBgUrDgMCGgUAoIGxMBgGCSqGSIb3DQEJAzELBgkq hkiG9w0BBwEwHAYJKoZIhvcNAQkFMQ8XDTAxMDUwMzE3MTIyN1owIwYJKoZIhvcNAQkEMRYE FDTzNQvX3SfIighWnKsFQGF5eG7IMFIGCSqGSIb3DQEJDzFFMEMwCgYIKoZIhvcNAwcwDgYI KoZIhvcNAwICAgCAMAcGBSsOAwIHMA0GCCqGSIb3DQMCAgFAMA0GCCqGSIb3DQMCAgEoMA0G CSqGSIb3DQEBAQUABIGAiagMOttagoARHNUzdIl38eCFxnnw2Ykk9EhNInJnfDPKG6CmfReC UwlYcxDChnPSIW+YC8gBjhBhCV1LPQcnQEPItlpWH5vfKzRzhRTlYDOlv4jAGzYzkIrsTSYG diKzUe4f10enDSMRJW6Ub7D7RWuc0yYqgohUKNWyGj0kRuw= --------------msEC7F884CEF164907A5775908-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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