Tag Archives: CPY

[$] A Gilectomy update

Post Syndicated from jake original https://lwn.net/Articles/754577/rss

In a rather short session at the 2018 Python Language Summit, Larry
Hastings updated attendees on the status of his Gilectomy project. The aim of that effort is
to remove the global
interpreter lock (GIL) from CPython. Since his status report at last year’s summit, little
has happened, which is part of why the session was so short. He hasn’t
given up on the overall idea, but it needs a new approach.

[$] Modifying the Python object model

Post Syndicated from jake original https://lwn.net/Articles/754163/rss

At the 2018 Python Language Summit, Carl Shapiro described some of
the experiments that he and others at Instagram did to look at ways to
improve the
performance of the CPython interpreter.
The talk was somewhat academic in tone and built on what has been learned
in other dynamic languages over the years. By modifying the Python object
model fairly substantially, they were able to roughly double the performance
of the “classic” Richards benchmark.

Voksi Releases Detailed Denuvo-Cracking Video Tutorial

Post Syndicated from Andy original https://torrentfreak.com/voksi-releases-detailed-denuvo-cracking-video-tutorial-180210/

Earlier this week, version 4.9 of the Denuvo anti-tamper system, which had protected Assassins Creed Origin for the past several months, was defeated by Italian cracking group CPY.

While Denuvo would probably paint four months of protection as a success, the company would certainly have preferred for things to have gone on a bit longer, not least following publisher Ubisoft’s decision to use VMProtect technology on top.

But while CPY do their thing in Italy there’s another rival whittling away at whatever the giants at Denuvo (and new owner Irdeto) can come up with. The cracker – known only as Voksi – hails from Bulgaria and this week he took the unusual step of releasing a 90-minute video (embedded below) in which he details how to defeat Denuvo’s V4 anti-tamper technology.

The video is not for the faint-hearted so those with an aversion to issues of a highly technical nature might feel the urge to look away. However, it may surprise readers to learn that not so long ago, Voksi knew absolutely nothing about coding.

“You will find this very funny and unbelievable,” Voksi says, recalling the events of 2012.

“There was one game called Sanctum and on one free [play] weekend [on Steam], I and my best friend played through it and saw how great the cooperative action was. When the free weekend was over, we wanted to keep playing, but we didn’t have any money to buy the game.

“So, I started to look for alternative ways, LAN emulators, anything! Then I decided I need to crack it. That’s how I got into reverse engineering. I started watching some shitty YouTube videos with bad quality and doing some tutorials. Then I found about Steam exploits and that’s how I got into making Steamworks fixes, allowing cracked multiplayer between players.”

Voksi says his entire cracking career began with this one indie game and his desire to play it with his best friend. Prior to that, he had absolutely no experience at all. He says he’s taken no university courses or any course at all for that matter. Everything he knows has come from material he’s found online. But the intrigue doesn’t stop there.

“I don’t even know how to code properly in high-level language like C#, C++, etc. But I understand assembly [language] perfectly fine,” he explains.

For those who code, that’s generally a little bit back to front, with low-level languages usually posing the most difficulties. But Voksi says that with assembly, everything “just clicked.”

Of course, it’s been six years since the 21-year-old was first motivated to crack a game due to lack of funds. In the more than half decade since, have his motivations changed at all? Is it the thrill of solving the puzzle or are there other factors at play?

“I just developed an urge to provide paid stuff for free for people who can’t afford it and specifically, co-op and multiplayer cracks. Of course, i’m not saying don’t support the developers if you have the money and like the game. You should do that,” he says.

“The challenge of cracking also motivates me, especially with an abomination like Denuvo. It is pure cancer for the gaming industry, it doesn’t help and it only causes issues for the paying customers.”

Those who follow Voksi online will know that as well as being known in his own right, he’s part of the REVOLT group, a collective that has Voksi’s core interests and goals as their own.

“REVOLT started as a group with one and only goal – to provide multiplayer support for cracked games. No other group was doing it until that day. It was founded by several members, from which I’m currently the only one active, still releasing cracks.

“Our great achievements are in first place, of course, cracking Denuvo V4, making us one of the four groups/people who were able to break the protection. In second place are our online fixes for several AAA games, allowing you to play on legit servers with legit players. In third place, our ordinary Steamworks fixes allowing you to play multiplayer between cracked users.”

In communities like /r/crackwatch on Reddit and those less accessible, Voksi and others doing similar work are often held up as Internet heroes, cracking games in order to give the masses access to something that might’ve been otherwise inaccessible. But how does this fame sit with him?

“Well, I don’t see myself as a hero, just another ordinary person doing what he loves. I love seeing people happy because of my work, that’s also a big motivation, but nothing more than that,” he says.

Finally, what’s up next for Voksi and what are his hopes for the rest of the year?

“In an ideal world, Denuvo would die. As for me, I don’t know, time will tell,” he concludes.

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Denuvo Has Been Sold to Global Anti-Piracy Outfit Irdeto

Post Syndicated from Andy original https://torrentfreak.com/denuvo-has-been-sold-to-global-anti-piracy-outfit-irdeto-180123/

It’s fair to say that of all video games anti-piracy technologies, Denuvo is perhaps the most hated of recent times. That hatred unsurprisingly stems from both its success and complexity.

Those with knowledge of the system say it’s fiendishly difficult to defeat but in recent times, cracks have been showing. In 2017, various iterations of the anti-tamper system were defeated by several cracking groups, much to the delight of the pirate masses.

Now, however, a new development has the potential to herald a new lease of life for the Austria-based anti-piracy company. A few moments ago it was revealed that the company has been bought by Irdeto, a global anti-piracy company with considerable heritage and resources.

“Irdeto has acquired Denuvo, the world leader in gaming security, to provide anti-piracy and anti-cheat solutions for games on desktop, mobile, console and VR devices,” Irdeto said in a statement.

“Denuvo provides technology and services for game publishers and platforms, independent software vendors, e-publishers and video publishers across the globe. Current Denuvo customers include Electronic Arts, UbiSoft, Warner Bros and Lionsgate Entertainment, with protection provided for games such as Star Wars Battlefront II, Football Manager, Injustice 2 and others.”

Irdeto says that Denuvo will “continue to operate as usual” with all of its staff retained – a total of 45 across Austria, Poland, the Czech Republic, and the US. Denuvo headquarters in Salzburg, Austria, will also remain intact along with its sales operations.

“The success of any game title is dependent upon the ability of the title to operate as the publisher intended,” says Irdeto CEO Doug Lowther.

“As a result, protection of both the game itself and the gaming experience for end users is critical. Our partnership brings together decades of security expertise under one roof to better address new and evolving security threats. We are looking forward to collaborating as a team on a number of initiatives to improve our core technology and services to better serve our customers.”

Denuvo was founded relatively recently in 2013 and employs less than 50 people. In contrast, Irdeto’s roots go all the way back to 1969 and currently has almost 1,000 staff. It’s a subsidiary of South Africa-based Internet and media group Naspers, a corporate giant with dozens of notable companies under its control.

While Denuvo is perhaps best known for its anti-piracy technology, Irdeto is also placing emphasis on the company’s ability to hinder cheating in online multi-player gaming environments. This has become a hot topic recently, with several lawsuits filed in the US by companies including Blizzard and Epic.

Denuvo CEO Reinhard Blaukovitsch

“Hackers and cybercriminals in the gaming space are savvy, and always have been. It is critical to implement robust security strategies to combat the latest gaming threats and protect the investment in games. Much like the movie industry, it’s the only way to ensure that great games continue to get made,” says Denuvo CEO Reinhard Blaukovitsch.

“In joining with Irdeto, we are bringing together a unique combination of security expertise, technology and enhanced piracy services to aggressively address security challenges that customers and gamers face from hackers.”

While it seems likely that the companies have been in negotiations for some, the timing of this announcement also coincides with negative news for Denuvo.

Yesterday it was revealed that the latest variant of its anti-tamper technology – Denuvo v4.8 – had been defeated by online cracking group CPY (Conspiracy). Version 4.8 had been protecting Sonic Forces since its release early November 2017 but the game was leaked out onto the Internet late Sunday with all protection neutralized.

Sonic Forces cracked by CPY

Irdeto has a long history of acquiring anti-piracy companies and technologies. They include Lockstream (DRM for content on mobile phones), Philips Cryptoworks (DVB conditional access system), Cloakware (various security), Entriq (media protection), BD+ (Blu-ray protection), and BayTSP (anti-piracy monitoring).

It’s also noteworthy that Irdeto supplied behind-the-scenes support in two of the largest IPTV provider raids of recent times, one focused on Spain in 2017 and more recently in Cyprus, Bulgaria, Greece and the Netherlands (1,2,3).

Source: TF, for the latest info on copyright, file-sharing, torrent sites and more. We also have VPN discounts, offers and coupons

[$] Who should see Python deprecation warnings?

Post Syndicated from corbet original https://lwn.net/Articles/740804/rss

As all Python developers discover sooner or later, Python is a rapidly
evolving language whose community occasionally makes changes that can break
existing programs. The switch to Python 3 is the most prominent
example, but minor releases can include significant changes as well. The
CPython interpreter can emit warnings for upcoming incompatible changes,
giving developers time to prepare their code, but those warnings are
suppressed and invisible by default. Work is afoot to make them visible,
but doing so is not as straightforward as it might seem.

The Evil Within 2 Used Denuvo, Then Dumped it Before Launch

Post Syndicated from Andy original https://torrentfreak.com/the-evil-within-2-used-denuvo-then-dumped-it-before-launch-171013/

At the end of September we reported on a nightmare scenario for videogame anti-tamper technology Denuvo.

With cracking groups chipping away at the system for the past few months, progressing in leaps and bounds, the race to the bottom was almost complete. After aiming to hold off pirates for the first few lucrative weeks and months after launch, the Denuvo-protected Total War: Warhammer 2 fell to pirates in a matter of hours.

In the less than two weeks that have passed since, things haven’t improved much. By most measurements, in fact, the situation appears to have gotten worse.

On Wednesday, action role-playing game Middle Earth: Shadow of War was cracked a day after launch. While this didn’t beat the record set by Warhammer 2, the scene was given an unexpected gift.

Instead of the crack appearing courtesy of scene groups STEAMPUNKS or CPY, which has largely been the tradition thus far this year, old favorite CODEX stepped up to the mark with their own efforts. This means there are now close to half a dozen entities with the ability to defeat Denuvo, which isn’t a good look for the anti-piracy outfit.

A CODEX crack for Denuvo, from nowhere

Needless to say, this development was met with absolute glee by pirates, who forgave the additional day taken to crack the game in order to welcome CODEX into the anti-Denuvo club. But while this is bad news for the anti-tamper technology, there could be a worse enemy crossing the horizon – no confidence.

This Tuesday, DSO Gaming reported that it had received a review copy of Bethesda’s then-upcoming survival horror game, The Evil Within 2. The site, which is often a reliable source for Denuvo-related news, confirmed that the code was indeed protected by Denuvo.

“Another upcoming title that will be using Denuvo is The Evil Within 2,” the site reported. “Bethesda has provided us with a review code for The Evil Within 2. As such, we can confirm that Denuvo is present in it.”

As you read this, October 13, 2017, The Evil Within 2 is enjoying its official worldwide launch. Early yesterday afternoon, however, the title leaked early onto the Internet, courtesy of cracking group CODEX.

At first view, it looked like CODEX had cracked Denuvo before the game’s official launch but the reality was somewhat different after the dust had settled. For reasons best known to developer Bethesda, Denuvo was completely absent from the title. As shown by the title’s NFO (information) file, the only protection present was that provided by Steam.

Denuvo? What Denuvo?

This raises a number of scenarios, none of them good for Denuvo.

One possibility is that all along Bethesda never intended to use Denuvo on the final release. Exactly why we’ll likely never know, but the theory doesn’t really gel with them including it in the review code reviewed by DSO Gaming earlier this week.

The other proposition is that Bethesda witnessed the fiasco around Denuvo’s ‘protection’ in recent days and decided not to invest in something that wasn’t going to provide value for money.

Of course, these theories are going to be pretty difficult to confirm. Denuvo are a pretty confident bunch when things are going their way but they go suspiciously quiet when the tide is turning. Equally, developers tend to keep quiet about their anti-piracy strategies too.

The bottom line though is that if the protection really works and turns in valuable cash, why wouldn’t Bethesda use it as they have done on previous titles including Doom and Prey?

With that question apparently answering itself at the moment, all eyes now turn to Denuvo. Although it has a history of being one of the most successful anti-piracy systems overall, it has taken a massive battering in recent times. Will it recover? Only time will tell but at the moment things couldn’t get much worse.

Source: TF, for the latest info on copyright, file-sharing, torrent sites and ANONYMOUS VPN services.

Denuvo Crisis After Total Warhammer 2 Gets Pirated in Hours

Post Syndicated from Andy original https://torrentfreak.com/denuvo-crisis-after-total-warhammer-2-gets-pirated-in-hours-170929/

Needing little introduction, the anti-piracy system sold by Denuvo Software Solutions of Austria is probably the most well-known product of its type of the planet.

For years, Denuvo was considered pretty much impenetrable, with its presence a virtual stamp of assurance that a game being protected by it would not fall victim to piracy, potentially for years. In recent times, however, things have begun to crumble.

Strangely, it started in early 2016 with bad news. Chinese cracking group 3DM declared that Denuvo was probably uncrackable and no protected games would appear online during the next two years.

By June, however, hope appeared on the horizon, with hints that progress was being made. By August 2016, all doubts were removed when a group called CONSPIR4CY (a reported collaboration between CPY and CODEX) released Rise of the Tomb Raider.

After that, Denuvo-protected titles began dropping like flies, with some getting cracked weeks after their launch. Then things got serious.

Early this year, Resident Evil 7 fell in less than a week. In the summer, RiME fell in a few days, four days exactly for Tekken 7.

Now, however, Denuvo has suffered its biggest failure yet, with strategy game Total War: Warhammer 2 falling to pirates in less than a day, arguably just a few hours. It was cracked by STEAMPUNKS, a group that’s been dumping cracked games on the Internet at quite a rate for the past few months.


“Take this advice, DO NOT CODE a new installer when you have very hot Babes dancing in their bikini just in front of you. Never again,” the group said in a statement. “This time we locked ourselves inside and produced a new installer.”

The fall of this game in such a short space of time will be of major concern to Denuvo Software Solutions. After Resident Evil 7 was cracked in days earlier this year, Denuvo Marketing Director Thomas Goebl told Eurogamer that some protection was better than nothing.

“Given the fact that every unprotected title is cracked on the day of release — as well as every update of games — our solution made a difference for this title,” he said.

With yesterday’s 0-day crack of Total War: Warhammer 2, it can be argued that Denuvo made absolutely no difference whatsoever to the availability of the title. It didn’t even protect the initial launch window.

Goebl’s additional comment in the summer was that “so far only one piracy group has been able to bypass [Denuvo].” Now, just a handful of months later, there are several groups with the ability. That’s not a good look for the company.

Back in 2016, Denuvo co-founder Robert Hernandez told Kotaku that the company does not give refunds. It would be interesting to know if anything has changed there too.

Source: TF, for the latest info on copyright, file-sharing, torrent sites and ANONYMOUS VPN services.

Cook: Security things in Linux v4.13

Post Syndicated from corbet original https://lwn.net/Articles/733095/rss

Kees Cook highlights
the security-related changes
in the 4.13 kernel.
Daniel Micay created a version of glibc’s FORTIFY_SOURCE
compile-time and run-time protection for finding overflows in the common
string (e.g. strcpy, strcmp) and memory (e.g. memcpy, memcmp)
functions. The idea is that since the compiler already knows the size of
many of the buffer arguments used by these functions, it can already build
in checks for buffer overflows. When all the sizes are known at compile
time, this can actually allow the compiler to fail the build instead of
continuing with a proven overflow. When only some of the sizes are known
(e.g. destination size is known at compile-time, but source size is only
known at run-time) run-time checks are added to catch any cases where an
overflow might happen. Adding this found several places where minor leaks
were happening, and Daniel and I chased down fixes for them.

[$] Rationalizing Python’s APIs

Post Syndicated from jake original https://lwn.net/Articles/727973/rss

CPython is the reference implementation of Python, so it is,
unsurprisingly, the target for various language-extension modules. But the
API and ABI it provides to those extensions ends up limiting what
alternative Python implementations—and even CPython itself—can do, since
those interfaces must continue to be supported. Beyond that, though, the
are not clearly delineated, so changes can unexpectedly affect extensions
that have come to depend on them. A recent thread on the python-ideas
mailing list looks at how to clean that situation up.

[$] Memory use in CPython and MicroPython

Post Syndicated from jake original https://lwn.net/Articles/725508/rss

At PyCon 2017, Kavya Joshi looked
at some of the differences between the Python reference implementation
(known as “CPython”) and
that of MicroPython. In particular,
she described the differences in memory use and handling between the two.
Those differences are
part of
what allows MicroPython to run on the severely memory-constrained
microcontrollers it targets—an environment that could never support CPython.

[$] Progress on the Gilectomy

Post Syndicated from jake original https://lwn.net/Articles/723514/rss

At the 2016 Python Language Summit, Larry Hastings introduced Gilectomy, his project to remove
the global interpreter lock (GIL) from CPython. The GIL serializes access
to the Python interpreter, so it severely limits the performance of
multi-threaded Python programs. At the 2017 summit, Hastings was back to
update attendees on the progress he has made and where Gilectomy is headed.

[$] New CPython workflow issues

Post Syndicated from jake original https://lwn.net/Articles/723418/rss

As part of a discussion in 2014 about where to host some of
the Python repositories,
Brett Cannon was delegated the task of determining where they should end
up. In early 2016, he decided that Python’s
code and
other repositories (e.g. PEPs) should land at GitHub;
at last year’s language
summit, he gave an overview of where things
stood with a few repositories that had made the conversion. Since that
time, the CPython
repository has made the switch and he wanted to discuss some of the
workflow issues surrounding that move at this year’s summit.

2017-02-22 FizzBuzz 2

Post Syndicated from Vasil Kolev original https://vasil.ludost.net/blog/?p=3343

Понеже идеята ми се мотае в главата от месец-два и тая нощ ми хрумна финалната оптимизация, ето продължението на post-а за fizzbuzz:

int i=0,p;
static void *pos[4]= {&&digit, &&fizz, &&buzz, &&fizzbuzz};
static void *loop[2] = { &&loopst, &&loopend};
int s3[3]={1,0,0},s5[5]={2,0,0,0,0};
char buff[2048];
char dgts[16]={'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'};
int buffpos=0;

	p= s3[i%3] | s5[i%5]; 
	goto *pos[p];

	memcpy(&buff[buffpos],"Fizz", 4);
	goto end;
	memcpy(&buff[buffpos],"Buzz", 4);
	goto end;
	memcpy(&buff[buffpos],"FizzBuzz", 8);
	goto end;
	goto *loop[i/100];
write(1, buff, buffpos);

Известно време се чудех как може цялото нещо да стане без никакъв branch, т.е. и без проверката за край на цикъла. Първоначалната ми идея беше да я карам на асемблер и да използвам като в exploit-ите NOP sled, нещо от типа (извинете ме за калпавия асемблер):

	JMP loopst
	JMP loopend
	; fizzbuzz implementation
	; i is in RAX

Или, накратко, колкото повече се увеличава i, толкова повече скачам назад с релативния JMP (който съм написал като вадене на нещо от EIP, което най-вероятно изобщо не е валидно), докато не ударя JMP, който ме изхвърля. Като оптимизация бях решил, че мога да shift-вам стойността с 4, така че sled-а да е само 25 броя.

В един момент ми хрумна, че мога да мина и без sled-а, като правя деление (което е отвратителна операция, но спестява кофа nop-ове). Така се получи по-горния вариант на C, който не е съвсем C, а просто някаква странна асемблероподобна гняс.

Иначе, важно е да се отбележи, че на какъвто и да е модерен процесор по-горния код е далеч по-неефективен от простото решение с if-ове, най-вече защото branch prediction и всички други екстри се справят много добре с всякаквите if-ове, но доста по-трудно могат да се сетят тия jmp-ове към таблици базирани на някакви стойности къде точно ще идат, за да се прави спекулативното изпълнение. Не съм си играл да benchmark-вам (въпреки, че имам желание), но като цяло горния код има шанс да се справя по-добре само на неща като 8086 и компания.

И като идея за следващата подобна мизерия, може би може да се оптимизира истински чрез ползване на някое от разширенията за работа с вектори/големи стойности и се unroll-не цикъла, например да се прави на стъпки от по 4 с някаква инструкция, която смята делители (кой-знае какви странни неща има вкарани вече в x86 instruction set-а).

Grumpy: Go running Python

Post Syndicated from corbet original http://lwn.net/Articles/710634/rss

The Google Open Source Blog introduces
the Grumpy project
. “Grumpy is an experimental Python runtime
for Go. It translates Python code into Go programs, and those transpiled
programs run seamlessly within the Go runtime. We needed to support a large
existing Python codebase, so it was important to have a high degree of
compatibility with CPython (quirks and all). The goal is for Grumpy to be a
drop-in replacement runtime for any pure-Python project.

systemd for Developers I

Post Syndicated from Lennart Poettering original http://0pointer.net/blog/projects/socket-activation.html

not only brings improvements for administrators and users, it also
brings a (small) number of new APIs with it. In this blog story (which might
become the first of a series) I hope to shed some light on one of the
most important new APIs in systemd:

Socket Activation

In the original blog
story about systemd
I tried to explain why socket activation is a
wonderful technology to spawn services. Let’s reiterate the background
here a bit.

The basic idea of socket activation is not new. The inetd
superserver was a standard component of most Linux and Unix systems
since time began: instead of spawning all local Internet services
already at boot, the superserver would listen on behalf of the
services and whenever a connection would come in an instance of the
respective service would be spawned. This allowed relatively weak
machines with few resources to offer a big variety of services at the
same time. However it quickly got a reputation for being somewhat
slow: since daemons would be spawned for each incoming connection a
lot of time was spent on forking and initialization of the services
— once for each connection, instead of once for them all.

Spawning one instance per connection was how inetd was primarily
used, even though inetd actually understood another mode: on the first
incoming connection it would notice this via poll() (or
select()) and spawn a single instance for all future
connections. (This was controllable with the
wait/nowait options.) That way the first connection
would be slow to set up, but subsequent ones would be as fast as with
a standalone service. In this mode inetd would work in a true
on-demand mode: a service would be made available lazily when it was

inetd’s focus was clearly on AF_INET (i.e. Internet) sockets. As
time progressed and Linux/Unix left the server niche and became
increasingly relevant on desktops, mobile and embedded environments
inetd was somehow lost in the troubles of time. Its reputation for
being slow, and the fact that Linux’ focus shifted away from only
Internet servers made a Linux machine running inetd (or one of its newer
implementations, like xinetd) the exception, not the rule.

When Apple engineers worked on optimizing the MacOS boot time they
found a new way to make use of the idea of socket activation: they
shifted the focus away from AF_INET sockets towards AF_UNIX
sockets. And they noticed that on-demand socket activation was only
part of the story: much more powerful is socket activation when used
for all local services including those which need to be started
anyway on boot. They implemented these ideas in launchd, a central building
block of modern MacOS X systems, and probably the main reason why
MacOS is so fast booting up.

But, before we continue, let’s have a closer look what the benefits
of socket activation for non-on-demand, non-Internet services in
detail are. Consider the four services Syslog, D-Bus, Avahi and the
Bluetooth daemon. D-Bus logs to Syslog, hence on traditional Linux
systems it would get started after Syslog. Similarly, Avahi requires
Syslog and D-Bus, hence would get started after both. Finally
Bluetooth is similar to Avahi and also requires Syslog and D-Bus but
does not interface at all with Avahi. Sinceoin a traditional
SysV-based system only one service can be in the process of getting
started at a time, the following serialization of startup would take
place: Syslog → D-Bus → Avahi → Bluetooth (Of course, Avahi and
Bluetooth could be started in the opposite order too, but we have to
pick one here, so let’s simply go alphabetically.). To illustrate
this, here’s a plot showing the order of startup beginning with system
startup (at the top).

Parallelization plot

Certain distributions tried to improve this strictly serialized
start-up: since Avahi and Bluetooth are independent from each other,
they can be started simultaneously. The parallelization is increased,
the overall startup time slightly smaller. (This is visualized in the
middle part of the plot.)

Socket activation makes it possible to start all four services
completely simultaneously, without any kind of ordering. Since the
creation of the listening sockets is moved outside of the daemons
themselves we can start them all at the same time, and they are able
to connect to each other’s sockets right-away. I.e. in a single step
the /dev/log and /run/dbus/system_bus_socket sockets
are created, and in the next step all four services are spawned
simultaneously. When D-Bus then wants to log to syslog, it just writes
its messages to /dev/log. As long as the socket buffer does
not run full it can go on immediately with what else it wants to do
for initialization. As soon as the syslog service catches up it will
process the queued messages. And if the socket buffer runs full then
the client logging will temporarily block until the socket is writable
again, and continue the moment it can write its log messages. That
means the scheduling of our services is entirely done by the kernel:
from the userspace perspective all services are run at the same time,
and when one service cannot keep up the others needing it will
temporarily block on their request but go on as soon as these
requests are dispatched. All of this is completely automatic and
invisible to userspace. Socket activation hence allows us to
drastically parallelize start-up, enabling simultaneous start-up of
services which previously were thought to strictly require
serialization. Most Linux services use sockets as communication
channel. Socket activation allows starting of clients and servers of
these channels at the same time.

But it’s not just about parallelization. It offers a number of
other benefits:

  • We no longer need to configure dependencies explicitly. Since the
    sockets are initialized before all services they are simply available,
    and no userspace ordering of service start-up needs to take place
    anymore. Socket activation hence drastically simplifies configuration
    and development of services.
  • If a service dies its listening socket stays around, not losing a
    single message. After a restart of the crashed service it can continue
    right where it left off.
  • If a service is upgraded we can restart the service while keeping
    around its sockets, thus ensuring the service is continously
    responsive. Not a single connection is lost during the upgrade.
  • We can even replace a service during runtime in a way that is
    invisible to the client. For example, all systems running systemd
    start up with a tiny syslog daemon at boot which passes all log
    messages written to /dev/log on to the kernel message
    buffer. That way we provide reliable userspace logging starting from
    the first instant of boot-up. Then, when the actual rsyslog daemon is
    ready to start we terminate the mini daemon and replace it with the
    real daemon. And all that while keeping around the original logging
    socket and sharing it between the two daemons and not losing a single
    message. Since rsyslog flushes the kernel log buffer to disk after
    start-up all log messages from the kernel, from early-boot and from
    runtime end up on disk.

For another explanation of this idea consult the original blog
story about systemd

Socket activation has been available in systemd since its
inception. On Fedora 15 a number of services have been modified to
implement socket activation, including Avahi, D-Bus and rsyslog (to continue with the example above).

systemd’s socket activation is quite comprehensive. Not only classic
sockets are support but related technologies as well:

  • AF_UNIX sockets, in the flavours SOCK_DGRAM, SOCK_STREAM and SOCK_SEQPACKET; both in the filesystem and in the abstract namespace
  • AF_INET sockets, i.e. TCP/IP and UDP/IP; both IPv4 and IPv6
  • Unix named pipes/FIFOs in the filesystem
  • AF_NETLINK sockets, to subscribe to certain kernel features. This
    is currently used by udev, but could be useful for other
    netlink-related services too, such as audit.
  • Certain special files like /proc/kmsg or device nodes like /dev/input/*.
  • POSIX Message Queues

A service capable of socket activation must be able to receive its
preinitialized sockets from systemd, instead of creating them
internally. For most services this requires (minimal)
patching. However, since systemd actually provides inetd compatibility
a service working with inetd will also work with systemd — which is
quite useful for services like sshd for example.

So much about the background of socket activation, let’s now have a
look how to patch a service to make it socket activatable. Let’s start
with a theoretic service foobard. (In a later blog post we’ll focus on
real-life example.)

Our little (theoretic) service includes code like the following for
creating sockets (most services include code like this in one way or

union {
        struct sockaddr sa;
        struct sockaddr_un un;
} sa;
int fd;

fd = socket(AF_UNIX, SOCK_STREAM, 0);
if (fd < 0) {
        fprintf(stderr, "socket(): %m\n");

memset(&sa, 0, sizeof(sa));
sa.un.sun_family = AF_UNIX;
strncpy(sa.un.sun_path, "/run/foobar.sk", sizeof(sa.un.sun_path));

if (bind(fd, &sa.sa, sizeof(sa)) < 0) {
        fprintf(stderr, "bind(): %m\n");

if (listen(fd, SOMAXCONN) < 0) {
        fprintf(stderr, "listen(): %m\n");

A socket activatable service may use the following code instead:

#include "sd-daemon.h"
int fd;

if (sd_listen_fds(0) != 1) {
        fprintf(stderr, "No or too many file descriptors received.\n");


systemd might pass you more than one socket (based on
configuration, see below). In this example we are interested in one
only. sd_listen_fds()
returns how many file descriptors are passed. We simply compare that
with 1, and fail if we got more or less. The file descriptors systemd
passes to us are inherited one after the other beginning with fd
#3. (SD_LISTEN_FDS_START is a macro defined to 3). Our code hence just
takes possession of fd #3.

As you can see this code is actually much shorter than the
original. This of course comes at the price that our little service
with this change will no longer work in a non-socket-activation
environment. With minimal changes we can adapt our example to work nicely
both with and without socket activation:

#include "sd-daemon.h"
int fd, n;

n = sd_listen_fds(0);
if (n > 1) {
        fprintf(stderr, "Too many file descriptors received.\n");
} else if (n == 1)
        fd = SD_LISTEN_FDS_START + 0;
else {
        union {
                struct sockaddr sa;
                struct sockaddr_un un;
        } sa;

        fd = socket(AF_UNIX, SOCK_STREAM, 0);
        if (fd < 0) {
                fprintf(stderr, "socket(): %m\n");

        memset(&sa, 0, sizeof(sa));
        sa.un.sun_family = AF_UNIX;
        strncpy(sa.un.sun_path, "/run/foobar.sk", sizeof(sa.un.sun_path));

        if (bind(fd, &sa.sa, sizeof(sa)) < 0) {
                fprintf(stderr, "bind(): %m\n");

        if (listen(fd, SOMAXCONN) < 0) {
                fprintf(stderr, "listen(): %m\n");

With this simple change our service can now make use of socket
activation but still works unmodified in classic environments. Now,
let’s see how we can enable this service in systemd. For this we have
to write two systemd unit files: one describing the socket, the other
describing the service. First, here’s foobar.socket:



And here’s the matching service file foobar.service:


If we place these two files in /etc/systemd/system we can
enable and start them:

# systemctl enable foobar.socket
# systemctl start foobar.socket

Now our little socket is listening, but our service not running
yet. If we now connect to /run/foobar.sk the service will be
automatically spawned, for on-demand service start-up. With a
modification of foobar.service we can start our service
already at startup, thus using socket activation only for
parallelization purposes, not for on-demand auto-spawning anymore:



And now let’s enable this too:

# systemctl enable foobar.service
# systemctl start foobar.service

Now our little daemon will be started at boot and on-demand,
whatever comes first. It can be started fully in parallel with its
clients, and when it dies it will be automatically restarted when it
is used the next time.

A single .socket file can include multiple ListenXXX stanzas, which
is useful for services that listen on more than one socket. In this
case all configured sockets will be passed to the service in the exact
order they are configured in the socket unit file. Also,
you may configure various socket settings in the .socket

In real life it’s a good idea to include description strings in
these unit files, to keep things simple we’ll leave this out of our
example. Speaking of real-life: our next installment will cover an
actual real-life example. We’ll add socket activation to the CUPS
printing server.

The sd_listen_fds() function call is defined in sd-daemon.h
and sd-daemon.c. These
two files are currently drop-in .c sources which projects should
simply copy into their source tree. Eventually we plan to turn this
into a proper shared library, however using the drop-in files allows
you to compile your project in a way that is compatible with socket
activation even without any compile time dependencies on
systemd. sd-daemon.c is liberally licensed, should compile
fine on the most exotic Unixes and the algorithms are trivial enough
to be reimplemented with very little code if the license should
nonetheless be a problem for your project. sd-daemon.c
contains a couple of other API functions besides
sd_listen_fds() that are useful when implementing socket
activation in a project. For example, there’s sd_is_socket()
which can be used to distuingish and identify particular sockets when
a service gets passed more than one.

Let me point out that the interfaces used here are in no way bound
directly to systemd. They are generic enough to be implemented in
other systems as well. We deliberately designed them as simple and
minimal as possible to make it possible for others to adopt similar

Stay tuned for the next installment. As mentioned, it will cover a
real-life example of turning an existing daemon into a
socket-activatable one: the CUPS printing service. However, I hope
this blog story might already be enough to get you started if you plan
to convert an existing service into a socket activatable one. We
invite everybody to convert upstream projects to this scheme. If you
have any questions join us on #systemd on freenode.