Date: Fri, 19 Apr 2024 17:48:01 +0200 From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@FreeBSD.org> To: Gerrit =?utf-8?Q?K=C3=BChn?= <gerrit.kuehn@aei.mpg.de> Cc: freebsd-stable@freebsd.org Subject: Re: possible regression handling packet fragmentation in 14.0 with tftp/pxe Message-ID: <86y1999wwe.fsf@ltc.des.dev> In-Reply-To: <20240419153951.5a23ce5f@arc.aei.uni-hannover.de> ("Gerrit =?utf-8?Q?K=C3=BChn=22's?= message of "Fri, 19 Apr 2024 15:39:51 %2B0200") References: <20240419153951.5a23ce5f@arc.aei.uni-hannover.de>
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Gerrit K=C3=BChn <gerrit.kuehn@aei.mpg.de> writes: > For the following: > 192.168.130.3 is the diskless client trying to boot (Linux) > 192.168.130.253 is the server for nfsroot and tftp (FreeBSD) > 192.168.130.254 is the router and dhcp-server (FreeBSD 13.3/14.0) > [...] > But this suspiciously looked like MTU problems. The VPN only offers an MTU > of 1425 by default, while tftp appears to use 1460. After some > searching and reading I found that the original tftp default was 512 byte > packets, and the client obviously requests larger packets for speed > reasons explicitely with the "blksize 1456" command. Unfortunately, I fou= nd > no way to configure the PXE firmware to use smaller packets. > However, adding the "-o" option to FreeBSD's tftpd could disable all extra > options and forced both the server and the client to user smaller packets. > TFTP and PXE-booting were working fine again after that change. Since you control the routers and endpoints, I would suggest running tcpdump at various points to see what is the tunnel and pf are doing to the UDP packets. They are presumably getting fragmented at some point, and hopefully reassembled somewhere else. Meanwhile you can also set the net.inet.udp.maxdgram sysctl to 1425 on the NFS server, as tftpd will cap the blocksize to that value. DES --=20 Dag-Erling Sm=C3=B8rgrav - des@FreeBSD.org
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