Date: Sat, 22 Jan 2000 18:37:17 -0800 From: Don Lewis <Don.Lewis@tsc.tdk.com> To: Brett Glass <brett@lariat.org>, Jason Young <jyoung@accessus.net> Cc: freebsd-security@FreeBSD.ORG Subject: RE: Some observations on stream.c and streamnt.c Message-ID: <200001230237.SAA18373@salsa.gv.tsc.tdk.com> In-Reply-To: <4.2.2.20000122071745.019bc4d0@localhost> References: <4.2.2.20000122071745.019bc4d0@localhost>
next in thread | previous in thread | raw e-mail | index | archive | help
On Jan 22, 7:50am, Brett Glass wrote: } Subject: RE: Some observations on stream.c and streamnt.c } >Envision a situation where somebody accidentally bumps the Big Red Button on } >ftp.cdrom.com, and immediately brings it back up. If it rate-limited its } >outgoing RSTs and hit this limit momentarily (and I really think this would } >be unlikely in the extreme if the RST rate-limiting threshold is } >reasonable), } } Would it be? Let's suppose that ftp.cdrom.com was handling 5000 connections } when you hit the switch. Within a second, you'd get AT LEAST 5000 packets to } which you'd need to respond with RSTs. Almost certainly more, due to } windowing. Actually, that's not true in this case because most of the clients will be doing downloads. The clients will only send packets upstream to ack the data they receive and to send download requests. While ftp.cdrom.com was comatose, the clients will probably all have acked the packets that were in flight and they will assume that ftp.cdrom.com will have seen these acks. For most of the clients, their downloads will appear to hang, and they will only find out that ftp.cdrom.com rebooted when they try to tell ftp.cdrom.com to abort the download. If the client is using TCP keepalives, it will eventually send a packet to ftp.cdrom.com on the stalled connection and will find out that ftp.cdrom.com rebooted when they get the RST, but the keepalive timer won't send a packet for quite a while, so this won't produce a flood of packets right after reboot. Clients sitting at the ftp prompt will find out the bad news as soon as they send their next ftp command. If a client downloading data from ftp.cdrom.com reboots and has RST totally disabled, this will stall the download of data and ftp.cdrom.com will keep resending the data until it eventually times out the connection because it never got an ACK. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200001230237.SAA18373>