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July 1, 2016 14:34 , by valessiobrito - | No one following this article yet.

Planet.Debian is a website that aggregates the blogs of many Debian contributors. Planet maintainers can be reached at planet at debian.org


John Goerzen: First Experiences with Stretch

June 22, 2017 13:19, by Planet Debian - 0no comments yet

I’ve done my first upgrades to Debian stretch at this point. The results have been overall good. On the laptop my kids use, I helped my 10-year-old do it, and it worked flawlessly. On my workstation, I got a kernel panic on boot. Hmm.

Unfortunately, my system has to use the nv drivers, which leaves me with an 80×25 text console. It took some finagling (break=init in grub, then manually insmoding the appropriate stuff based on modules.dep for nouveau), but finally I got a console so I could see what was breaking. It appeared that init was crashing because it couldn’t find liblz4. A little digging shows that liblz4 is in /usr, and /usr wasn’t mounted. I’ve filed the bug on systemd-sysv for this.

I run root on ZFS, and further digging revealed that I had datasets named like this:

  • tank/hostname-1/ROOT
  • tank/hostname-1/usr
  • tank/hostname-1/var

This used to be fine. The mountpoint property of the usr dataset put it at /usr without incident. But it turns out that this won’t work now, unless I set ZFS_INITRD_ADDITIONAL_DATASETS in /etc/default/zfs for some reason. So I renamed them so usr was under ROOT, and then the system booted.

Then I ran samba not liking something in my bind interfaces line (to be fair, it did still say eth0 instead of br0). rpcbind was failing in postinst, though a reboot seems to have helped that. More annoying was that I had trouble logging into my system because resolv.conf was left empty (despite dns-* entries in /etc/network/interfaces and the presence of resolvconf). I eventually repaired that, and found that it kept removing my “search” line. Eventually I removed resolvconf.

Then mariadb’s postinst was silently failing. I eventually discovered it was sending info to syslog (odd), and /etc/init.d/apparmor teardown let it complete properly. It seems like there may have been an outdated /etc/apparmor.d/cache/usr.sbin.mysql out there for some reason.

Then there was XFCE. I use it with xmonad, and the session startup was really wonky. I had to zap my sessions, my panel config, etc. and start anew. I am still not entirely sure I have it right, but I at do have a usable system now.



Dirk Eddelbuettel: nanotime 0.2.0

June 22, 2017 12:16, by Planet Debian - 0no comments yet

A new version of the nanotime package for working with nanosecond timestamps just arrived on CRAN.

nanotime uses the RcppCCTZ package for (efficient) high(er) resolution time parsing and formatting up to nanosecond resolution, and the bit64 package for the actual integer64 arithmetic.

Thanks to a metric ton of work by Leonardo Silvestri, the package now uses S4 classes internally allowing for greater consistency of operations on nanotime objects.

Changes in version 0.2.0 (2017-06-22)

  • Rewritten in S4 to provide more robust operations (#17 by Leonardo)

  • Ensure tz="" is treated as unset (Leonardo in #20)

  • Added format and tz arguments to nanotime, format, print (#22 by Leonardo and Dirk)

  • Ensure printing respect options()$max.print, ensure names are kept with vector (#23 by Leonardo)

  • Correct summary() by defining names<- (Leonardo in #25 fixing #24)

  • Report error on operations that are meaningful for type; handled NA, NaN, Inf, -Inf correctly (Leonardo in #27 fixing #26)

We also have a diff to the previous version thanks to CRANberries. More details and examples are at the nanotime page; code, issue tickets etc at the GitHub repository.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. Please report excessive re-aggregation in third-party for-profit settings.



Norbert Preining: Signal handling in R

June 22, 2017 8:28, by Planet Debian - 0no comments yet

Recently I have been programming quite a lot in R, and today stumbled over the problem to implement a kind of monitoring loop in R. Typically that would be a infinite loop with sleep calls, but I wanted to allow for waking up from the sleep via sending UNIX style signals, in particular SIGINT. After some searching I found Beyond Exception Handling: Conditions and Restarts from the Advanced R book. But it didn’t really help me a lot to program an interrupt handler.

My requirements were:

  • an interruption of the work-part should be immediately restarted
  • an interruption of the sleep-part should go immediately into the work-part

Unfortunately it seems not to be possible to ignore interrupts at all from with the R code. The best one can do is install interrupt handlers and try to repeat the code which was executed while the interrupt happened. This is what I tried to implement with the following code below. I still have to digest the documentation about conditions and restarts, and play around a lot, but at least this is an initial working version.

workfun <- function() {
  i <- 1
  do_repeat <- FALSE
  while (TRUE) {
    message("begin of the loop")
    withRestarts(
      {
        # do all the work here
        cat("Entering work part i =", i, "\n");
        Sys.sleep(10)
        i <- i + 1
        cat("finished work part\n")
      }, 
      gotSIG = function() { 
        message("interrupted while working, restarting work part")
        do_repeat <<- TRUE
        NULL
      }
    )
    if (do_repeat) {
      cat("restarting work loop\n")
      do_repeat <- FALSE
      next
    } else {
      cat("between work and sleep part\n")
    }
    withRestarts(
      {
        # do the sleep part here
        cat("Entering sleep part i =", i, "\n")
        Sys.sleep(10)
        i <- i + 1
        cat("finished sleep part\n")
      }, 
      gotSIG = function() {
        message("got work to do, waking up!")
        NULL
      }
    )
    message("end of the loop")
  }
}

cat("Current process:", Sys.getpid(), "\n");

withCallingHandlers({
    workfun()
  },
  interrupt = function(e) {
    invokeRestart("gotSIG")
  })

While not perfect, I guess I have to live with this method for now.



Dirk Eddelbuettel: RcppCCTZ 0.2.3 (and 0.2.2)

June 22, 2017 1:06, by Planet Debian - 0no comments yet

A new minor version 0.2.3 of RcppCCTZ is now on CRAN.

RcppCCTZ uses Rcpp to bring CCTZ to R. CCTZ is a C++ library for translating between absolute and civil times using the rules of a time zone. In fact, it is two libraries. One for dealing with civil time: human-readable dates and times, and one for converting between between absolute and civil times via time zones. The RcppCCTZ page has a few usage examples and details.

This version ensures that we set the TZDIR environment variable correctly on the old dreaded OS that does not come with proper timezone information---an issue which had come up while preparing the next (and awesome, trust me) release of nanotime. It also appears that I failed to blog about 0.2.2, another maintenance release, so changes for both are summarised next.

Changes in version 0.2.3 (2017-06-19)

  • On Windows, the TZDIR environment variable is now set in .onLoad()

  • Replaced init.c with registration code inside of RcppExports.cpp thanks to Rcpp 0.12.11.

Changes in version 0.2.2 (2017-04-20)

  • Synchronized with upstream CCTZ

  • The time_point object is instantiated explicitly for nanosecond use which appears to be required on macOS

We also have a diff to the previous version thanks to CRANberries. More details are at the RcppCCTZ page; code, issue tickets etc at the GitHub repository.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. Please report excessive re-aggregation in third-party for-profit settings.



Joey Hess: DIY professional grade solar panel installation

June 21, 2017 22:42, by Planet Debian - 0no comments yet

I've installed 1 kilowatt of solar panels on my roof, using professional grade eqipment. The four panels are Astronergy 260 watt panels, and they're mounted on IronRidge XR100 rails. Did it all myself, without help.

house with 4 solar panels on roof

I had three goals for this install:

  1. Cheap but sturdy. Total cost will be under $2500. It would probably cost at least twice as much to get a professional install, and the pros might not even want to do such a small install.
  2. Learn the roof mount system. I want to be able to add more panels, remove panels when working on the roof, and understand everything.
  3. Make every day a sunny day. With my current solar panels, I get around 10x as much power on a sunny day as a cloudy day, and I have plenty of power on sunny days. So 10x the PV capacity should be a good amount of power all the time.

My main concerns were, would I be able to find the rafters when installing the rails, and would the 5x3 foot panels be too unweildly to get up on the roof by myself.

I was able to find the rafters, without needing a stud finder, after I removed the roof's vent caps, which exposed the rafters. The shingles were on straight enough that I could follow the lines down and drilled into the rafter on the first try every time. And I got the rails on spaced well and straight, although I could have spaced the FlashFeet out better (oops).

My drill ran out of juice half-way, and I had to hack it to recharge on solar power, but that's another story. Between the learning curve, a lot of careful measurement, not the greatest shoes for roofing, and waiting for recharging, it took two days to get the 8 FlashFeet installed and the rails mounted.

Taking a break from that and swimming in the river, I realized I should have been wearing my water shoes on the roof all along. Super soft and nubbly, they make me feel like a gecko up there! After recovering from an (unrelated) achilles tendon strain, I got the panels installed today.

Turns out they're not hard to handle on the roof by myself. Getting them up a ladder to the roof by yourself would normally be another story, but my house has a 2 foot step up from the back retaining wall to the roof, and even has a handy grip beam as you step up.

roof next to the ground with a couple of cinderblock steps

The last gotcha, which I luckily anticipated, is that panels will slide down off the rails before you can get them bolted down. This is where a second pair of hands would have been most useful. But, I macguyvered a solution, attaching temporary clamps before bringing a panel up, that stopped it sliding down while I was attaching it.

clamp temporarily attached to side of panel

I also finished the outside wiring today. Including the one hack of this install so far. Since the local hardware store didn't have a suitable conduit to bring the cables off the roof, I cobbled one together from pipe, with foam inserts to prevent chafing.

some pipe with 5 wires running through it, attached to the side of the roof

While I have 1 kilowatt of power on my roof now, I won't be able to use it until next week. After ordering the upgrade, I realized that my old PWM charge controller would be able to handle less than half the power, and to get even that I would have needed to mount the fuse box near the top of the roof and run down a large and expensive low-voltage high-amperage cable, around OO AWG size. Instead, I'll be upgrading to a MPPT controller, and running a single 150 volt cable to it.

Then, since the MPPT controller can only handle 1 kilowatt when it's converting to 24 volts, not 12 volts, I'm gonna have to convert the entire house over from 12V DC to 24V DC, including changing all the light fixtures and rewiring the battery bank...



Reproducible builds folks: Reproducible Builds: week 112 in Stretch cycle

June 21, 2017 16:27, by Planet Debian - 0no comments yet

Here's what happened in the Reproducible Builds effort between Sunday June 11 and Saturday June 17 2017:

Upcoming events

Upstream patches and bugs filed

Reviews of unreproducible packages

1 package review has been added, 19 have been updated and 2 have been removed in this week, adding to our knowledge about identified issues.

Weekly QA work

During our reproducibility testing, FTBFS bugs have been detected and reported by:

  • Adrian Bunk (1)
  • Edmund Grimley Evans (1)

diffoscope development

tests.reproducible-builds.org

As you might have noticed, Debian stretch was released last week. Since then, Mattia and Holger renamed our testing suite to stretch and added a buster suite so that we keep our historic results for stretch visible and can continue our development work as usual. In this sense, happy hacking on buster; may it become the best Debian release ever and hopefully the first reproducible one!

  • Vagrant Cascadian:
  • Valerie Young: Add highlighting in navigation for the new nodes health pages.
  • Mattia Rizzolo:
    • Do not dump database ACL in the backups.
    • Deduplicate SSLCertificateFile directive into the common-directives-ssl macro
    • Apache: t.r-b.o: redirect /testing/ to /stretch/
    • db: s/testing/stretch/g
    • Start adding code to test buster...
  • Holger Levsen:
    • Update README.infrastructure to explain who has root access where.
    • reproducible_nodes_info.sh: correctly recognize zero builds per day.
    • Add build nodes health overview page, then split it in three: health overview, daily munin graphs and weekly munin graphs.
    • reproducible_worker.sh: improve handling of systemctl timeouts.
    • reproducible_build_service: sleep less and thus restart failed workers sooner.
    • Replace ftp.(de|uk|us).debian.org with deb.debian.org everywhere.
    • Performance page: also show local problems with _build_service.sh (which are autofixed after a maximum of 133.7 minutes).
    • Rename nodes_info job to html_nodes_info.
    • Add new node health check jobs, split off from maintenance jobs, run every 15 minutes.
      • Add two new checks: 1. for correct future (2019 is incorrect atm, and we sometimes got that). 2.) for writeable /tmp (sometimes happens on borked armhf nodes).
    • Add jobs for testing buster.
    • s/testing/stretch/g in all the code.
    • Finish the code to deal with buster.
    • Teach jessie and Ubuntu 16.04 how to debootstrap buster.

Axel Beckert is currently in the process of setting up eight LeMaker HiKey960 boards. These boards were sponsored by Hewlett Packard Enterprise and will be hosted by the SOSETH students association at ETH Zurich. Thanks to everyone involved here and also thanks to Martin Michlmayr and Steve Geary who initiated getting these boards to us.

Misc.

This week's edition was written by Chris Lamb, Holger Levsen & reviewed by a bunch of Reproducible Builds folks on IRC & the mailing lists.



Vincent Bernat: IPv4 route lookup on Linux

June 21, 2017 8:00, by Planet Debian - 0no comments yet

TL;DR: With its implementation of IPv4 routing tables using LPC-tries, Linux offers good lookup performance (50 ns for a full view) and low memory usage (64 MiB for a full view).


During the lifetime of an IPv4 datagram inside the Linux kernel, one important step is the route lookup for the destination address through the fib_lookup() function. From essential information about the datagram (source and destination IP addresses, interfaces, firewall mark, …), this function should quickly provide a decision. Some possible options are:

  • local delivery (RTN_LOCAL),
  • forwarding to a supplied next hop (RTN_UNICAST),
  • silent discard (RTN_BLACKHOLE).

Since 2.6.39, Linux stores routes into a compressed prefix tree (commit 3630b7c050d9). In the past, a route cache was maintained but it has been removed1 in Linux 3.6.

Route lookup in a trie

Looking up a route in a routing table is to find the most specific prefix matching the requested destination. Let’s assume the following routing table:

$ ip route show scope global table 100
default via 203.0.113.5 dev out2
192.0.2.0/25
        nexthop via 203.0.113.7  dev out3 weight 1
        nexthop via 203.0.113.9  dev out4 weight 1
192.0.2.47 via 203.0.113.3 dev out1
192.0.2.48 via 203.0.113.3 dev out1
192.0.2.49 via 203.0.113.3 dev out1
192.0.2.50 via 203.0.113.3 dev out1

Here are some examples of lookups and the associated results:

Destination IP Next hop
192.0.2.49 203.0.113.3 via out1
192.0.2.50 203.0.113.3 via out1
192.0.2.51 203.0.113.7 via out3 or 203.0.113.9 via out4 (ECMP)
192.0.2.200 203.0.113.5 via out2

A common structure for route lookup is the trie, a tree structure where each node has its parent as prefix.

Lookup with a simple trie

The following trie encodes the previous routing table:

Simple routing trie

For each node, the prefix is known by its path from the root node and the prefix length is the current depth.

A lookup in such a trie is quite simple: at each step, fetch the nth bit of the IP address, where n is the current depth. If it is 0, continue with the first child. Otherwise, continue with the second. If a child is missing, backtrack until a routing entry is found. For example, when looking for 192.0.2.50, we will find the result in the corresponding leaf (at depth 32). However for 192.0.2.51, we will reach 192.0.2.50/31 but there is no second child. Therefore, we backtrack until the 192.0.2.0/25 routing entry.

Adding and removing routes is quite easy. From a performance point of view, the lookup is done in constant time relative to the number of routes (due to maximum depth being capped to 32).

Quagga is an example of routing software still using this simple approach.

Lookup with a path-compressed trie

In the previous example, most nodes only have one child. This leads to a lot of unneeded bitwise comparisons and memory is also wasted on many nodes. To overcome this problem, we can use path compression: each node with only one child is removed (except if it also contains a routing entry). Each remaining node gets a new property telling how many input bits should be skipped. Such a trie is also known as a Patricia trie or a radix tree. Here is the path-compressed version of the previous trie:

Patricia trie

Since some bits have been ignored, on a match, a final check is executed to ensure all bits from the found entry are matching the input IP address. If not, we must act as if the entry wasn’t found (and backtrack to find a matching prefix). The following figure shows two IP addresses matching the same leaf:

Lookup in a Patricia trie

The reduction on the average depth of the tree compensates the necessity to handle those false positives. The insertion and deletion of a routing entry is still easy enough.

Many routing systems are using Patricia trees:

Lookup with a level-compressed trie

In addition to path compression, level compression2 detects parts of the trie that are densily populated and replace them with a single node and an associated vector of 2k children. This node will handle k input bits instead of just one. For example, here is a level-compressed version our previous trie:

Level-compressed trie

Such a trie is called LC-trie or LPC-trie and offers higher lookup performances compared to a radix tree.

An heuristic is used to decide how many bits a node should handle. On Linux, if the ratio of non-empty children to all children would be above 50% when the node handles an additional bit, the node gets this additional bit. On the other hand, if the current ratio is below 25%, the node loses the responsibility of one bit. Those values are not tunable.

Insertion and deletion becomes more complex but lookup times are also improved.

Implementation in Linux

The implementation for IPv4 in Linux exists since 2.6.13 (commit 19baf839ff4a) and is enabled by default since 2.6.39 (commit 3630b7c050d9).

Here is the representation of our example routing table in memory3:

Memory representation of a trie

There are several structures involved:

The trie can be retrieved through /proc/net/fib_trie:

$ cat /proc/net/fib_trie
Id 100:
  +-- 0.0.0.0/0 2 0 2
     |-- 0.0.0.0
        /0 universe UNICAST
     +-- 192.0.2.0/26 2 0 1
        |-- 192.0.2.0
           /25 universe UNICAST
        |-- 192.0.2.47
           /32 universe UNICAST
        +-- 192.0.2.48/30 2 0 1
           |-- 192.0.2.48
              /32 universe UNICAST
           |-- 192.0.2.49
              /32 universe UNICAST
           |-- 192.0.2.50
              /32 universe UNICAST
[...]

For internal nodes, the numbers after the prefix are:

  1. the number of bits handled by the node,
  2. the number of full children (they only handle one bit),
  3. the number of empty children.

Moreover, if the kernel was compiled with CONFIG_IP_FIB_TRIE_STATS, some interesting statistics are available in /proc/net/fib_triestat4:

$ cat /proc/net/fib_triestat
Basic info: size of leaf: 48 bytes, size of tnode: 40 bytes.
Id 100:
        Aver depth:     2.33
        Max depth:      3
        Leaves:         6
        Prefixes:       6
        Internal nodes: 3
          2: 3
        Pointers: 12
Null ptrs: 4
Total size: 1  kB
[...]

When a routing table is very dense, a node can handle many bits. For example, a densily populated routing table with 1 million entries packed in a /12 can have one internal node handling 20 bits. In this case, route lookup is essentially reduced to a lookup in a vector.

The following graph shows the number of internal nodes used relative to the number of routes for different scenarios (routes extracted from an Internet full view, /32 routes spreaded over 4 different subnets with various densities). When routes are densily packed, the number of internal nodes are quite limited.

Internal nodes and null pointers

Performance

So how performant is a route lookup? The maximum depth stays low (about 6 for a full view), so a lookup should be quite fast. With the help of a small kernel module, we can accurately benchmark5 the fib_lookup() function:

Maximum depth and lookup time

The lookup time is loosely tied to the maximum depth. When the routing table is densily populated, the maximum depth is low and the lookup times are fast.

When forwarding at 10 Gbps, the time budget for a packet would be about 50 ns. Since this is also the time needed for the route lookup alone in some cases, we wouldn’t be able to forward at line rate with only one core. Nonetheless, the results are pretty good and they are expected to scale linearly with the number of cores.

Another interesting figure is the time it takes to insert all those routes into the kernel. Linux is also quite efficient in this area since you can insert 2 million routes in less than 10 seconds:

Insertion time

Memory usage

The memory usage is available directly in /proc/net/fib_triestat. The statistic provided doesn’t account for the fib_info structures, but you should only have a handful of them (one for each possible next-hop). As you can see on the graph below, the memory use is linear with the number of routes inserted, whatever the shape of the routes is.

Memory usage

The results are quite good. With only 256 MiB, about 2 million routes can be stored!

Routing rules

Unless configured without CONFIG_IP_MULTIPLE_TABLES, Linux supports several routing tables and has a system of configurable rules to select the table to use. These rules can be configured with ip rule. By default, there are three of them:

$ ip rule show
0:      from all lookup local
32766:  from all lookup main
32767:  from all lookup default

Linux will first lookup for a match in the local table. If it doesn’t find one, it will lookup in the main table and at last resort, the default table.

Builtin tables

The local table contains routes for local delivery:

$ ip route show table local
broadcast 127.0.0.0 dev lo proto kernel scope link src 127.0.0.1
local 127.0.0.0/8 dev lo proto kernel scope host src 127.0.0.1
local 127.0.0.1 dev lo proto kernel scope host src 127.0.0.1
broadcast 127.255.255.255 dev lo proto kernel scope link src 127.0.0.1
broadcast 192.168.117.0 dev eno1 proto kernel scope link src 192.168.117.55
local 192.168.117.55 dev eno1 proto kernel scope host src 192.168.117.55
broadcast 192.168.117.63 dev eno1 proto kernel scope link src 192.168.117.55

This table is populated automatically by the kernel when addresses are configured. Let’s look at the three last lines. When the IP address 192.168.117.55 was configured on the eno1 interface, the kernel automatically added the appropriate routes:

  • a route for 192.168.117.55 for local unicast delivery to the IP address,
  • a route for 192.168.117.255 for broadcast delivery to the broadcast address,
  • a route for 192.168.117.0 for broadcast delivery to the network address.

When 127.0.0.1 was configured on the loopback interface, the same kind of routes were added to the local table. However, a loopback address receives a special treatment and the kernel also adds the whole subnet to the local table. As a result, you can ping any IP in 127.0.0.0/8:

$ ping -c1 127.42.42.42
PING 127.42.42.42 (127.42.42.42) 56(84) bytes of data.
64 bytes from 127.42.42.42: icmp_seq=1 ttl=64 time=0.039 ms

--- 127.42.42.42 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.039/0.039/0.039/0.000 ms

The main table usually contains all the other routes:

$ ip route show table main
default via 192.168.117.1 dev eno1 proto static metric 100
192.168.117.0/26 dev eno1 proto kernel scope link src 192.168.117.55 metric 100

The default route has been configured by some DHCP daemon. The connected route (scope link) has been automatically added by the kernel (proto kernel) when configuring an IP address on the eno1 interface.

The default table is empty and has little use. It has been kept when the current incarnation of advanced routing has been introduced in Linux 2.1.68 after a first tentative using “classes” in Linux 2.1.156.

Performance

Since Linux 4.1 (commit 0ddcf43d5d4a), when the set of rules is left unmodified, the main and local tables are merged and the lookup is done with this single table (and the default table if not empty). Without specific rules, there is no performance hit when enabling the support for multiple routing tables. However, as soon as you add new rules, some CPU cycles will be spent for each datagram to evaluate them. Here is a couple of graphs demonstrating the impact of routing rules on lookup times:

Routing rules impact on performance

For some reason, the relation is linear when the number of rules is between 1 and 100 but the slope increases noticeably past this threshold. The second graph highlights the negative impact of the first rule (about 30 ns).

A common use of rules is to create virtual routers: interfaces are segregated into domains and when a datagram enters through an interface from domain A, it should use routing table A:

# ip rule add iif vlan457 table 10
# ip rule add iif vlan457 blackhole
# ip rule add iif vlan458 table 20
# ip rule add iif vlan458 blackhole

The blackhole rules may be removed if you are sure there is a default route in each routing table. For example, we add a blackhole default with a high metric to not override a regular default route:

# ip route add blackhole default metric 9999 table 10
# ip route add blackhole default metric 9999 table 20
# ip rule add iif vlan457 table 10
# ip rule add iif vlan458 table 20

To reduce the impact on performance when many interface-specific rules are used, interfaces can be attached to VRF instances and a single rule can be used to select the appropriate table:

# ip link add vrf-A type vrf table 10
# ip link set dev vrf-A up
# ip link add vrf-B type vrf table 20
# ip link set dev vrf-B up
# ip link set dev vlan457 master vrf-A
# ip link set dev vlan458 master vrf-B
# ip rule show
0:      from all lookup local
1000:   from all lookup [l3mdev-table]
32766:  from all lookup main
32767:  from all lookup default

The special l3mdev-table rule was automatically added when configuring the first VRF interface. This rule will select the routing table associated to the VRF owning the input (or output) interface.

VRF was introduced in Linux 4.3 (commit 193125dbd8eb), the performance was greatly enhanced in Linux 4.8 (commit 7889681f4a6c) and the special routing rule was also introduced in Linux 4.8 (commit 96c63fa7393d, commit 1aa6c4f6b8cd). You can find more details about it in the kernel documentation.

Conclusion

The takeaways from this article are:

  • route lookup times hardly increase with the number of routes,
  • densily packed /32 routes lead to amazingly fast route lookups,
  • memory use is low (128 MiB par million routes),
  • no optimization is done on routing rules.

  1. The routing cache was subject to reasonably easy to launch denial of service attacks. It was also believed to not be efficient for high volume sites like Google but I have first-hand experience it was not the case for moderately high volume sites. 

  2. IP-address lookup using LC-tries”, IEEE Journal on Selected Areas in Communications, 17(6):1083-1092, June 1999. 

  3. For internal nodes, the key_vector structure is embedded into a tnode structure. This structure contains information rarely used during lookup, notably the reference to the parent that is usually not needed for backtracking as Linux keeps the nearest candidate in a variable. 

  4. One leaf can contain several routes (struct fib_alias is a list). The number of “prefixes” can therefore be greater than the number of leaves. The system also keeps statistics about the distribution of the internal nodes relative to the number of bits they handle. In our example, all the three internal nodes are handling 2 bits. 

  5. The measurements are done in a virtual machine with one vCPU. The host is an Intel Core i5-4670K running at 3.7 GHz during the experiment (CPU governor was set to performance). The kernel is Linux 4.11. The benchmark is single-threaded. It runs a warm-up phase, then executes about 100,000 timed iterations and keeps the median. Timings of individual runs are computed from the TSC

  6. Fun fact: the documentation of this first tentative of more flexible routing is still available in today’s kernel tree and explains the usage of the “default class”



Steve McIntyre: So, Stretch happened...

June 20, 2017 22:21, by Planet Debian - 0no comments yet

Things mostly went very well, and we've released Debian 9 this weekend past. Many many people worked together to make this possible, and I'd like to extend my own thanks to all of them.

As a project, we decided to dedicate Stretch to our late founder Ian Murdock. He did much of the early work to get Debian going, and inspired many more to help him. I had the good fortune to meet up with Ian years ago at a meetup attached to a Usenix conference, and I remember clearly he was a genuinely nice guy with good ideas. We'll miss him.

For my part in the release process, again I was responsible for producing our official installation and live images. Release day itself went OK, but as is typical the process ran late into Saturday night / early Sunday morning. We made and tested lots of different images, although numbers were down from previous releases as we've stopped making the full CD sets now.

Sunday was the day for the the release party in Cambridge. As is traditional, a group of us met up at a local hostelry for some revelry! We hid inside the pub to escape from the ridiculouly hot weather we're having at the moment.

Party

Due to a combination of the lack of sleep and the heat, I nearly forgot to even take any photos - apologies to the extra folks who'd been around earlier whom I missed with the camera... :-(



Andreas Bombe: New Blog

June 20, 2017 22:09, by Planet Debian - 0no comments yet

So I finally got myself a blog to write about my software and hardware projects, my work in Debian and, I guess, stuff. Readers of planet.debian.org, hi! If you can see this I got the configuration right.

For the curious, I’m using a static site generator for this blog — Hugo to be specific — like all the cool kids do these days.



Foteini Tsiami: Internationalization, part one

June 20, 2017 10:00, by Planet Debian - 0no comments yet

The first part of internationalizing a Greek application, is, of course, translating all the Greek text to English. I already knew how to open a user interface (.ui) file with Glade and how to translate/save it from there, and mail the result to the developers.

If only it was that simple! I learned that the code of most open source software is kept on version control systems, which fortunately are a bit similar to Wikis, which I was familiar with, so I didn’t have a lot of trouble understanding the concepts. Thanks to a very brief git crash course from my mentors, I was able to quickly start translating, committing, and even pushing back the updated files.

The other tricky part was internationalizing the python source code. There Glade couldn’t be used, a text editor like Pluma was needed. And the messages were part of the source code, so I had to be extra careful not to break the syntax. The English text then needed to be wrapped around _(), which does the gettext call which dynamically translates the messages into the user language.

All this was very educative, but now that the first part of the internationalization, i.e. the Greek-to-English translations, are over, I think I’ll take some time to read more about the tools that I used!




Norbert Preining: TeX Live 2017 hits Debian/unstable

June 20, 2017 1:09, by Planet Debian - 1One comment

Yesterday I uploaded the first packages of TeX Live 2017 to Debian/unstable, meaning that the new release cycle has started. Debian/stretch was released over the weekend, and this opened up unstable for new developments. The upload comprised the following packages: asymptote, cm-super, context, context-modules, texlive-base, texlive-bin, texlive-extra, texlive-extra, texlive-lang, texworks, xindy.

I mentioned already in a previous post the following changes:

  • several packages have been merged, some are dropped (eg. texlive-htmlxml) and one new package (texlive-plain-generic) has been added
  • luatex got updated to 1.0.4, and is now considered stable
  • updmap and fmtutil now require either -sys or -user
  • tlmgr got a shell mode (interactive/scripting interface) and a new feature to add arbitrary TEXMF trees (conf auxtrees)

The last two changes are described together with other news (easy TEXMF tree management) in the TeX Live release post. These changes more or less sum up the new infra structure developments in TeX Live 2017.

Since the last release to unstable (which happened in 2017-01-23) about half a year of package updates have accumulated, below is an approximate list of updates (not split into new/updated, though).

Enjoy the brave new world of TeX Live 2017, and please report bugs to the BTS!

Updated/new packages:
academicons, achemso, acmart, acro, actuarialangle, actuarialsymbol, adobemapping, alkalami, amiri, animate, aomart, apa6, apxproof, arabluatex, archaeologie, arsclassica, autoaligne, autobreak, autosp, axodraw2, babel, babel-azerbaijani, babel-english, babel-french, babel-indonesian, babel-japanese, babel-malay, babel-ukrainian, bangorexam, baskervaldx, baskervillef, bchart, beamer, beamerswitch, bgteubner, biblatex-abnt, biblatex-anonymous, biblatex-archaeology, biblatex-arthistory-bonn, biblatex-bookinother, biblatex-caspervector, biblatex-cheatsheet, biblatex-chem, biblatex-chicago, biblatex-claves, biblatex-enc, biblatex-fiwi, biblatex-gb7714-2015, biblatex-gost, biblatex-ieee, biblatex-iso690, biblatex-manuscripts-philology, biblatex-morenames, biblatex-nature, biblatex-opcit-booktitle, biblatex-oxref, biblatex-philosophy, biblatex-publist, biblatex-shortfields, biblatex-subseries, bibtexperllibs, bidi, biochemistry-colors, bookcover, boondox, bredzenie, breqn, bxbase, bxcalc, bxdvidriver, bxjalipsum, bxjaprnind, bxjscls, bxnewfont, bxorigcapt, bxpapersize, bxpdfver, cabin, callouts, chemfig, chemformula, chemmacros, chemschemex, childdoc, circuitikz, cje, cjhebrew, cjk-gs-integrate, cmpj, cochineal, combofont, context, conv-xkv, correctmathalign, covington, cquthesis, crimson, crossrefware, csbulletin, csplain, csquotes, css-colors, cstldoc, ctex, currency, cweb, datetime2-french, datetime2-german, datetime2-romanian, datetime2-ukrainian, dehyph-exptl, disser, docsurvey, dox, draftfigure, drawmatrix, dtk, dviinfox, easyformat, ebproof, elements, endheads, enotez, eqnalign, erewhon, eulerpx, expex, exsheets, factura, facture, fancyhdr, fbb, fei, fetamont, fibeamer, fithesis, fixme, fmtcount, fnspe, fontmfizz, fontools, fonts-churchslavonic, fontspec, footnotehyper, forest, gandhi, genealogytree, glossaries, glossaries-extra, gofonts, gotoh, graphics, graphics-def, graphics-pln, grayhints, gregoriotex, gtrlib-largetrees, gzt, halloweenmath, handout, hang, heuristica, hlist, hobby, hvfloat, hyperref, hyperxmp, ifptex, ijsra, japanese-otf-uptex, jlreq, jmlr, jsclasses, jslectureplanner, karnaugh-map, keyfloat, knowledge, komacv, koma-script, kotex-oblivoir, l3, l3build, ladder, langsci, latex, latex2e, latex2man, latex3, latexbug, latexindent, latexmk, latex-mr, leaflet, leipzig, libertine, libertinegc, libertinus, libertinust1math, lion-msc, lni, longdivision, lshort-chinese, ltb2bib, lualatex-math, lualibs, luamesh, luamplib, luaotfload, luapackageloader, luatexja, luatexko, lwarp, make4ht, marginnote, markdown, mathalfa, mathpunctspace, mathtools, mcexam, mcf2graph, media9, minidocument, modular, montserrat, morewrites, mpostinl, mptrees, mucproc, musixtex, mwcls, mweights, nameauth, newpx, newtx, newtxtt, nfssext-cfr, nlctdoc, novel, numspell, nwejm, oberdiek, ocgx2, oplotsymbl, optidef, oscola, overlays, pagecolor, pdflatexpicscale, pdfpages, pdfx, perfectcut, pgfplots, phonenumbers, phonrule, pkuthss, platex, platex-tools, polski, preview, program, proofread, prooftrees, pst-3dplot, pst-barcode, pst-eucl, pst-func, pst-ode, pst-pdf, pst-plot, pstricks, pstricks-add, pst-solides3d, pst-spinner, pst-tools, pst-tree, pst-vehicle, ptex2pdf, ptex-base, ptex-fontmaps, pxbase, pxchfon, pxrubrica, pythonhighlight, quran, ran_toks, reledmac, repere, resphilosophica, revquantum, rputover, rubik, rutitlepage, sansmathfonts, scratch, seealso, sesstime, siunitx, skdoc, songs, spectralsequences, stackengine, stage, sttools, studenthandouts, svg, tcolorbox, tex4ebook, tex4ht, texosquery, texproposal, thaienum, thalie, thesis-ekf, thuthesis, tikz-kalender, tikzmark, tikz-optics, tikz-palattice, tikzpeople, tikzsymbols, titlepic, tl17, tqft, tracklang, tudscr, tugboat-plain, turabian-formatting, txuprcal, typoaid, udesoftec, uhhassignment, ukrainian, ulthese, unamthesis, unfonts-core, unfonts-extra, unicode-math, uplatex, upmethodology, uptex-base, urcls, variablelm, varsfromjobname, visualtikz, xassoccnt, xcharter, xcntperchap, xecjk, xepersian, xetexko, xevlna, xgreek, xsavebox, xsim, ycbook.



Jeremy Bicha: GNOME Tweak Tool 3.25.3

June 19, 2017 23:15, by Planet Debian - 0no comments yet

Today I released the second development snapshot (3.25.3) of what will be GNOME Tweak Tool 3.26.

I consider the initial User Interface (UI) rework proposed by the GNOME Design Team to be complete now. Every page in Tweak Tool has been updated, either in this snapshot or the previous development snapshot.

The hard part still remains: making the UI look as good as the mockups. Tweak Tool’s backend makes this a bit more complicated than usual for an app like this.

Here are a few visual highlights of this release.

The Typing page has been moved into an Additional Layout Options dialog in the Keyboard & Mouse page. Also, the Compose Key option has been given its own dialog box.

Florian Müllner added content to the Extensions page that is shown if you don’t have any GNOME Shell extensions installed yet.

A hidden feature that GNOME has had for a long time is the ability to move the Application Menu from the GNOME top bar to a button in the app’s title bar. This is easy to enable in Tweak Tool by turning off the Application Menu switch in the Top Bar page. This release improves how well that works, especially for Ubuntu users where the required hidden appmenu window button was probably not pre-configured.

Some of the ComboBoxes have been replaced by ListBoxes. One example is on the Workspaces page where the new design allows for more information about the different options. The ListBoxes are also a lot easier to select than the smaller ComboBoxes were.

For details of these and other changes, see the commit log or the NEWS file.

GNOME Tweak Tool 3.26 will be released alongside GNOME 3.26 in mid-September.



Shirish Agarwal: Seizures, Vigo and bi-pedal motion

June 19, 2017 16:49, by Planet Debian - 0no comments yet

Dear all, an update is in order. While talking to physiotherapist couple of days before, came to know the correct term to what was I experiencing. I had experienced convulsive ‘seizure‘ , spasms being a part of it. Reading the wikipedia entry and the associated links/entries it seems I am and was very very lucky.

The hospital or any hospital is a very bad bad place. I have seen all horror movies which people say are disturbing but have never been disturbed as much as I was in hospital. I couldn’t help but hear people’s screams and saw so many cases which turned critical. At times it was not easy to remain positive but dunno from where there was a will to live which pushed me and is still pushing me.

One of the things that was painful for a long time were the almost constant stream of injections that were injected in me. It was almost an afterthought that the nurse put a Vigo in me.

Similar to the Vigo injected in me.

While the above medical device is similar, mine had a cross, the needle was much shorter and is injected into the vein. After that all injections are injected into that including common liquid which is salt,water and something commonly given to patients to stabilize first. I am not remembering the name atm.

I also had a urine bag which was attached to my penis in a non-invasive manner. Both my grandfather and grandma used to cry when things went wrong while I didn’t feel any pain but when the urine bag was disattached and attached again, so seems things have improved there.

I was also very conscious of getting bed sores as both my grandpa and grandma had them when in hospital. As I had no strength I had to beg. plead do everything to make sure that every few hours I was turned from one side to other. I also had an air bag which is supposed to alleviate or relief this condition.

Constant physiotherapy every day for a while slowly increased my strength and slowly both the vigo and feeding tube put inside my throat was removed.

I have no remembrance as to when they had put the feeding tube as it was all rubber and felt bad when it came out.

Further physiotherapy helped me crawl till the top of the bed, the bed was around 6 feet in length and and more than enough so I could turn both sides without falling over.

Few days later I found I could also sit up using my legs as a lever and that gave confidence to the doctors to remove the air bed so I could crawl more easily.

Couple of more days later I stood on my feet for the first time and it was like I had lead legs. Each step was painful but the sense and feeling of independence won over whatever pain was there.

I had to endure wet wipes from nurses and ward boys in place of a shower everyday and while they were respectful always it felt humiliating.

The first time I had a bath after 2 weeks or something, every part of my body cried and I felt like a weakling. I had thought I wouldn’t be able to do justice to the physiotherapy session which was soon after but after the session was back to feeling normal.

For a while I was doing the penguin waddle which while painful was also had humor in it. I did think of shooting the penguin waddle but decided against it as I was half-naked most of the time ( the hospital clothes never fit me properly)

Cut to today and I was able to climb up and down the stairs on my own and circled my own block, slowly but was able to do it on my own by myself.

While I always had a sense of wonderment for bi-pedal motion as well as all other means of transport, found much more respect of walking. I live near a fast food eating joint so I see lot of youngsters posing in different ways with their legs to show interest to their mates. And this I know happens both on the conscious and sub-conscious levels. To be able to see and discern that also put a sense of wonder in nature’s creations.

All in all, I’m probabl6y around 40% independent and still 60% interdependent. I know I have to be patient with myself and those around me and explain to others what I’m going through.

For e.g. I still tend to spill things and still can’t touch-type much.

So, the road is long, I can only pray and hope best wishes for anybody who is my condition and do pray that nobody goes through what I went through, especiallly not children.

I am also hoping that things like DxtER and range of non-invasive treatments make their way into India and the developing world at large.

Anybody who is overweight and is either disgusted or doesn’t like the gym route, would recommend doing sessions with a physiotherapist that you can trust. You have to trust that her judgement will push you a bit more and not more that the gains you make are toppled over.

I still get dizziness spells while doing therapy but will to break it as I know dizziness doesn’t help me.

I hope my writings give strength and understanding to either somebody who is going through it, or relatives or/and caregivers so they know the mental status of the person who’s going through it.

Till later and sorry it became so long.

Update – I forgot to share this inspirational story from my city which I shared with a friend days ago. Add to that, she is from my city. What it doesn’t share is that Triund is a magical place. I had visited once with a friend who had elf ears (he had put on elf ears) and it is kind of place which alchemist talks about, a place where imagination does turn wild and there is magic in the air.


Filed under: Miscellenous Tagged: #air bag, #bed sores, #convulsive epileptic seizure, #crawling, #horror, #humiliation, #nakedness, #penguin waddle, #physiotherapy, #planet-debian, #spilling things, #urine bag, #Vigo medical device

Vasudev Kamath: Update: - Shell pipelines with subprocess crate and use of Exec::shell function

June 19, 2017 15:18, by Planet Debian - 0no comments yet

In my previous post I used Exec::shell function from subprocess crate and passed it string generated by interpolating --author argument. This string was then run by the shell via Exec::shell. After publishing post I got ping on IRC by Jonas Smedegaard and Paul Wise that I should replace Exec::shell, as it might be prone to errors or vulnerabilities of shell injection attack. Indeed they were right, in hurry I did not completely read the function documentation which clearly mentions this fact.

When invoking this function, be careful not to interpolate arguments into the string run by the shell, such as Exec::shell(format!("sort {}", filename)). Such code is prone to errors and, if filename comes from an untrusted source, to shell injection attacks. Instead, use Exec::cmd("sort").arg(filename).

Though I'm not directly taking input from untrusted source, its still possible that the string I got back from git log command might contain some oddly formatted string with characters of different encoding which could possibly break the Exec::shell , as I'm not sanitizing the shell command. When we use Exec::cmd and pass argument using .args chaining, the library takes care of creating safe command line. So I went in and modified the function to use Exec::cmd instead of Exec::shell.

Below is updated function.

fn copyright_fromgit(repo: &str) -> Result<Vec<String>> {
    let tempdir = TempDir::new_in(".", "debcargo")?;
    Exec::cmd("git")
     .args(&["clone", "--bare", repo, tempdir.path().to_str().unwrap()])
     .stdout(subprocess::NullFile)
     .stderr(subprocess::NullFile)
     .popen()?;

    let author_process = {
        Exec::shell(OsStr::new("git log --format=\"%an <%ae>\"")).cwd(tempdir.path()) |
        Exec::shell(OsStr::new("sort -u"))
    }.capture()?;
    let authors = author_process.stdout_str().trim().to_string();
    let authors: Vec<&str> = authors.split('\n').collect();
    let mut notices: Vec<String> = Vec::new();
    for author in &authors {
        let author_string = format!("--author={}", author);
        let first = {
            Exec::cmd("/usr/bin/git")
             .args(&["log", "--format=%ad",
                    "--date=format:%Y",
                    "--reverse",
                    &author_string])
             .cwd(tempdir.path()) | Exec::shell(OsStr::new("head -n1"))
        }.capture()?;

        let latest = {
            Exec::cmd("/usr/bin/git")
             .args(&["log", "--format=%ad", "--date=format:%Y", &author_string])
             .cwd(tempdir.path()) | Exec::shell("head -n1")
        }.capture()?;

        let start = i32::from_str(first.stdout_str().trim())?;
        let end = i32::from_str(latest.stdout_str().trim())?;
        let cnotice = match start.cmp(&end) {
            Ordering::Equal => format!("{}, {}", start, author),
            _ => format!("{}-{}, {}", start, end, author),
        };

        notices.push(cnotice);
    }

    Ok(notices)
}

I still use Exec::shell for generating author list, this is not problematic as I'm not interpolating arguments to create command string.



Hideki Yamane: PoC: use Sphinx for debian-policy

June 19, 2017 13:09, by Planet Debian - 0no comments yet

Before party, we did a monthly study meeting and I gave a talk about tiny hack for debian-policy document.

debian-policy was converted from debian-sgml to docbook in 4.0.0, and my proposal is "Go move forward to Sphinx".

Here's sample, and you can also get PoC source from my GitHub repo and check it.