Currently we use a single hash table per PCB database for connected and bound PCBs. Since we started using net_epoch to synchronize hash table lookups, there's been a bug, noted in a comment above in_pcbrehash(): connecting a socket can cause an inpcb to move between hash chains, and this can cause a concurrent lookup to follow the wrong linkage pointers. I believe this could cause rare, spurious ECONNREFUSED errors in the worse case. Address the problem by introducing a second hash table and adding more linkage pointers to struct inpcb. Now the database has one table each for connected and unconnected sockets. When inserting an inpcb into the hash table, in_pcbinhash() now looks at the foreign address of the inpcb to figure out which table to use. This ensures that queue linkage pointers are stable until the socket is disconnected, so the problem described above goes away. There is also a small benefit in that in_pcblookup_*() can now search just one of the two possible hash buckets. I also made the "rehash" parameter of in(6)_pcbconnect() unused. This parameter seems confusing and it is simpler to let the inpcb code figure out what to do using the existing INP_INHASHLIST flag. UDP sockets pose a special problem since they can be connected and disconnected multiple times during their lifecycle. To handle this, the patch plugs a hole in the inpcb structure and uses it to store an SMR sequence number. When an inpcb is disconnected - an operation which requires the global PCB database hash lock - the write sequence number is advanced, and in order to reconnect, the connecting thread must wait for readers to drain before reusing the inpcb's hash chain linkage pointers. raw_ip (ab)uses the hash table without using the corresponding accessors. Since there are now two hash tables, it arbitrarily uses the "connected" table for all of its PCBs. This will be addressed in some way in the future. inp interators which specify a hash bucket will only visit connected PCBs. This is not really correct, but nothing in the tree uses that functionality except raw_ip, which as mentioned above places all of its PCBs in the "connected" table and so is unaffected. Discussed with: glebius Tested by: glebius Sponsored by: Klara, Inc. Sponsored by: Modirum MDPay Differential Revision: https://reviews.freebsd.org/D38569 |
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.cirrus-ci | ||
.github | ||
bin | ||
cddl | ||
contrib | ||
crypto | ||
etc | ||
gnu | ||
include | ||
kerberos5 | ||
lib | ||
libexec | ||
release | ||
rescue | ||
sbin | ||
secure | ||
share | ||
stand | ||
sys | ||
targets | ||
tests | ||
tools | ||
usr.bin | ||
usr.sbin | ||
.arcconfig | ||
.arclint | ||
.cirrus.yml | ||
.clang-format | ||
.git-blame-ignore-revs | ||
.gitattributes | ||
.gitignore | ||
CONTRIBUTING.md | ||
COPYRIGHT | ||
LOCKS | ||
MAINTAINERS | ||
Makefile | ||
Makefile.inc1 | ||
Makefile.libcompat | ||
Makefile.sys.inc | ||
ObsoleteFiles.inc | ||
README.md | ||
RELNOTES | ||
UPDATING |
FreeBSD Source:
This is the top level of the FreeBSD source directory.
FreeBSD is an operating system used to power modern servers, desktops, and embedded platforms. A large community has continually developed it for more than thirty years. Its advanced networking, security, and storage features have made FreeBSD the platform of choice for many of the busiest web sites and most pervasive embedded networking and storage devices.
For copyright information, please see the file COPYRIGHT in this directory. Additional copyright information also exists for some sources in this tree - please see the specific source directories for more information.
The Makefile in this directory supports a number of targets for building components (or all) of the FreeBSD source tree. See build(7), config(8), FreeBSD handbook on building userland, and Handbook for kernels for more information, including setting make(1) variables.
For information on the CPU architectures and platforms supported by FreeBSD, see the FreeBSD website's Platforms page.
Source Roadmap:
Directory | Description |
---|---|
bin | System/user commands. |
cddl | Various commands and libraries under the Common Development and Distribution License. |
contrib | Packages contributed by 3rd parties. |
crypto | Cryptography stuff (see crypto/README). |
etc | Template files for /etc. |
gnu | Commands and libraries under the GNU General Public License (GPL) or Lesser General Public License (LGPL). Please see gnu/COPYING and gnu/COPYING.LIB for more information. |
include | System include files. |
kerberos5 | Kerberos5 (Heimdal) package. |
lib | System libraries. |
libexec | System daemons. |
release | Release building Makefile & associated tools. |
rescue | Build system for statically linked /rescue utilities. |
sbin | System commands. |
secure | Cryptographic libraries and commands. |
share | Shared resources. |
stand | Boot loader sources. |
sys | Kernel sources (see sys/README.md). |
targets | Support for experimental DIRDEPS_BUILD |
tests | Regression tests which can be run by Kyua. See tests/README for additional information. |
tools | Utilities for regression testing and miscellaneous tasks. |
usr.bin | User commands. |
usr.sbin | System administration commands. |
For information on synchronizing your source tree with one or more of the FreeBSD Project's development branches, please see FreeBSD Handbook.