From owner-freebsd-questions Mon Nov 27 19:30:50 2000 Delivered-To: freebsd-questions@freebsd.org Received: from boreas.isi.edu (boreas.isi.edu [128.9.160.161]) by hub.freebsd.org (Postfix) with ESMTP id 8ADC737B479 for ; Mon, 27 Nov 2000 19:30:46 -0800 (PST) Received: from isi.edu (hbo.isi.edu [128.9.160.75]) by boreas.isi.edu (8.9.3/8.9.3) with ESMTP id TAA22907 for ; Mon, 27 Nov 2000 19:30:46 -0800 (PST) Message-ID: <3A2326E6.AD835284@isi.edu> Date: Mon, 27 Nov 2000 19:30:46 -0800 From: Lars Eggert Organization: USC Information Sciences Institute X-Mailer: Mozilla 4.76 [en] (X11; U; Linux 2.2.12 i386) X-Accept-Language: en, de MIME-Version: 1.0 To: questions@freebsd.org Subject: send(2) and resuming after ENOBUFS Content-Type: multipart/signed; protocol="application/x-pkcs7-signature"; micalg=sha1; boundary="------------ms45365CBC2B7361633B763B1E" Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG This is a cryptographically signed message in MIME format. --------------ms45365CBC2B7361633B763B1E Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Hi, for an experiment, I'm writing a little tool that blasts large (9K) UDP packets at another host. I'm using connected sockets and send(2). Very quickly, send(2) returns indicating that the socket send buffer is full. So far, so good. My question is: How do I detect that the socket buffer has sufficiently emptied to resume sending? I tried setting the SO_SNDLOWAT to my message size and checking with select(2) if the socket is writable. However, select(2) always returns telling me it is, even though a following send(2) results in ENOBUFS. This may in fact be a bug in FreeBSD, since the setsockopt(2) man page seems to indicate that this should work: SO_SNDLOWAT is an option to set the minimum count for output operations. Most output operations process all of the data supplied by the call, de- livering data to the protocol for transmission and blocking as necessary for flow control. Nonblocking output operations will process as much da- ta as permitted subject to flow control without blocking, but will pro- cess no data if flow control does not allow the smaller of the low water mark value or the entire request to be processed. A select(2) operation testing the ability to write to a socket will return true only if the low water mark amount could be processed. The default value for SO_SNDLOWAT is set to a convenient size for network efficiency, often 1024. Any ideas? Spinning is not really an option... Thanks, Lars -- Lars Eggert Information Sciences Institute http://www.isi.edu/larse/ University of Southern California --------------ms45365CBC2B7361633B763B1E 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 hkiG9w0BBwEwHAYJKoZIhvcNAQkFMQ8XDTAwMTEyODAzMzA0NlowIwYJKoZIhvcNAQkEMRYE FDIoBirT7xtBuJxc67bikT4t+jlJMFIGCSqGSIb3DQEJDzFFMEMwCgYIKoZIhvcNAwcwDgYI KoZIhvcNAwICAgCAMAcGBSsOAwIHMA0GCCqGSIb3DQMCAgFAMA0GCCqGSIb3DQMCAgEoMA0G CSqGSIb3DQEBAQUABIGAyyJN2hwBjbx0tuHNaSP/4VPJlTtJztcpY8E2Pms3jVdZa/fWrpjN itcH2bIg3biDku5Th/sWhadic7vPSIHIWL+5ty0SCXKE+CuZ6op68aYtY9jqHEyVk8QDAf/Z 9TqHJ1zgqm9/Qw6+k5z/9zbX6KpG8V22TVVbAnwhV6Q/p+Y= --------------ms45365CBC2B7361633B763B1E-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message