Once Again - Encryption and Authentication

For a new MANET protocol I started to verify the security concept. Not from a security point of view, rather from a protocol feasibility point of view. The security concept is based on existing security protocols. I just removed dynamic components like key exchange and the like (to be correct: dynamic aspects are done by special messages and not that tight linked with the protocol). The result should be a very lean TLV, containing only required security data without padding issues are “reserved” bits....

September 6, 2012 · 2 min · Hagen Paul Pfeifer

Safe Arrays and Pointers for C

John Nagle (no, not the TCP Nagle ;-) proposed a extension to C to keep array information over the call context to do bounds checks. His proposal Safe Arrays and Pointers for C through compatible additions to the language is a nice reading. On the GCC maillinglist the responses are mixed: more questions and doubts if such a extension will and can be adopted by the users.

September 5, 2012 · 1 min · Hagen Paul Pfeifer

Vacation in Vallis/Switzerland

In the 32nd week I am on vacation in Switzerland in the mountains of Vallis. The picture is taken in Lötschental and the lake is called Schwarzsee. Only a few meters from our accommodation. The photo is taken by daoro

August 5, 2012 · 1 min · Hagen Paul Pfeifer

x86 Floating Point

x86 Floating Point was and still is a source of problems. First of all the FPU (floating point coprocessor, x87) has 8 registers. Via gdb and info all-register you can display the floating point register. These registers are all 80 bit wide. And here the problems start: standardized are floating point math with 32 or 64 bit (float or double). If you compile the next construct with -m32 on a 32bit and a 64bit arch the results will differ:...

August 1, 2012 · 2 min · Hagen Paul Pfeifer

If Ping was Designed by the Git People

net-ping host --no=dns,bind --proto=TCP,rfc:492 eth0@ipv4:: -ADDR.ARPA --stats -v ;-) from https://twitter.com/gitHater

July 30, 2012 · 1 min · Hagen Paul Pfeifer

TCPM Agenda for IETF-84 Vancouver Meeting

Michael published the agenda for TCPM Vancouver Meeting and there are lot of items on the list this time. The following list is sorted by personal interest: Proportional Rate Reduction for TCP TCP Fast Open Increasing TCP’s Initial Window Impact of IW10 on Interactive Real-Time Communication Additional negotiation in the TCP Timestamp Option field during the TCP handshake TCP and SCTP RTO Restart More Accurate ECN Feedback in TCP TCP Loss Probe (TLP): An Algorithm for Fast Recovery of Tail Losses Evaluating TCP Laminar Highly Efficient Selective Acknowledgement (SACK) for TCP Shared Use of Experimental TCP Options A TCP Authentication Option NAT Extension RFC 1323bis HOST_ID TCP Options: Implementation and Preliminary Test Results Shared Memory Communications over RDMA Processing of IP Security/Compartment and Precedence Information by TCP Processing of TCP segments with Mirrored End-points I am especially interested in Ilpo’s Interactive Real-Time Communication IW10 talk....

July 25, 2012 · 1 min · Hagen Paul Pfeifer

3.5 Released

Just a few bugfixes goes in since -rc7 so here we go: Linux 3.5 released. Changeset of upcoming 3.6 should be smaller because of vacation period.

July 22, 2012 · 1 min · Hagen Paul Pfeifer

Compiler Block Reordering and Memory Layout Optimization

GCC as enabled with -freorder-blocks and a optimization level larger 1 will reorder instructions at a block level. This optimization is mainly to compress correlated code to provide a optimized cache aware memory layout. Because of some Linux kernel hacking I forced to get the details when and where GCC’s optimizations kicks in. The most effective way for userland programs without branch-taken-knowledge is through profile guided optimization nowadays. But this is not possible in every setup (lack of realistic input data, …)....

July 22, 2012 · 2 min · Hagen Paul Pfeifer

Epson WP 4535 - Multi-Function Inkjet and Linux

Today I buyed a new printer: Epson WP 4535. The printer can scan up to 600 DPI to a USB device (as JPEG or PDF). A nice feature because I dont want to install sane or any other scaner software. Printing works out of the box via CUPS. No additional driver installation required. My room mate tried to test the printer with Windows which failed. Under Windows you must download the actual driver from Epson Homepage....

July 19, 2012 · 1 min · Hagen Paul Pfeifer

IETF I-D and RFC News

Vancouver is near so there was a lot of I-D submission progress. I-D cutoff is over so ID submission settles. Subsequent a list of some interesting I-D’s (this list is sorted): A Roadmap for Transmission Control Protocol (TCP) Specification Documents An IPv4 Flowlabel Option Operational Issues with Tunnel Maximum Transmission Unit (MTU) Accurate ECN Feedback Option in TCP Implications of running Internet over ports 80 and 443 OSPFv3 Auto-Configuration Cache DNS Server Selection on the Dual-stack Home Network An Acceptable Use Policy for New ICMP Types and Codes How to Write an RTP Payload Format Definitions of Managed Objects for Packet Sampling IPv6 Guidance for Internet Content and Application Service Providers Formally Deprecating some IPv4 Options Client Identifier Option in DHCP Server Replies TCP Extensions for High Performance IPv6 Path MTU Updates Host Identity Protocol Architecture Domain Names in Application-Layer Protocols From TCP perspective not that much....

July 19, 2012 · 4 min · Hagen Paul Pfeifer