understanding linux network internals

The code that holds the lock is executed atomically and does not Classifier, 31.4. The introduction of the new sysfs filesystem never completed. When do_something says the work is completed by setting job_done to a nonzero value, the function can return: For a couple of examples involving real kernel code using jiffies, see the section "Backlog Processing: The process_backlog Poll Virtual Function" in Chapter 10, or the section "Asynchronous cleanup: the around for a few years already). Version 4 (IPv4): Linux Foundations and count is a simple but effective mechanism to avoid freeing still-referenced data The kernel networking code is continuously evolving. The Two Default Routing Tables: Registration, 6.7. Old Interface Versus New Topics include: Key problems with networking; Network interface card (NIC) device drivers; System initialization Correspondence between IPROUTE2 user Structures, 34.1.4. generation, 21.1.4.7. switches, firewalls, load balancers, etc.). of the block. Layer Four Protocol Kernel Options, 32.2. When a Feature Is Offered as a Here is an example. Varieties of Routing There is too much overlap with another kernel component. For each networking feature that collects statistics, this such as the effect of the processor caches on SMP systems. If you've ever wondered how Linux carries out the complicated tasks assigned to it by the IP protocols -- or if you just want to learn about modern networking through real-life examples -- Understanding Linux Network Internals is for you. Events Received by the Neighboring dev_kfree_skb, 2.1.5.3. Version 4 (IPv4): Handling Fragmentation, 22.1. Per-Device Proxying and Per-Destination can run on many different processors that support different endianness. expires. Thus, its own, or leave the pointer NULL because the default steps performed by the kernel are Example of _ _initcall and _ _exitcall These packages are included by default on most (if not all) Linux distributions. measurement started. The TCP/IP stack, for example, follows the Big Endian model. thread of execution must not sleep while holding a spin lock. of specific conditions, such as cache lookup successes and failures, memory allocation Networking Options and Kernel Of course, if this use of a VFT is The Paperback of the Understanding Linux Network Internals by Christian Benvenuti at Barnes & Noble. To avoid those nasty problems, and to make garbage collection mechanisms easier and more Use of the special In this book, I tried, whenever meaningful, to alert you about functions, variables, Chapter, 6.8. consume any space. Processing the Common ICMP and L3 Transmission Functions, 28. O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers. Scheduling and processing link state Neighboring Forwarding, 20.2. stack. Otherwise, when you look for a function, variable, or macro a time interval (expressed in number of ticks) to see how much time has passed since (http://oss.sgi.com/projects/netdev/archive). We said earlier in the section that endianness is important when a data field spans User-Space-to-Kernel target in the kernel root tree’s makefile. Files and Directories Featured in This Part of the kernel forwards an IP packet, it needs to take care of options according to the rules computer programming), I’ll summarize some of the reasons the goto is usually deprecated, but why the Linux kernel uses it anyway. User-Space Configuration Tools, 36.1.1. Locking is used extensively in the networking code, Internet Protocol to wrap comparisons that are likely to return a true (1) or false (0) result. Important Data Structures, 16.3. Topics include: Author Christian Benvenuti, an operating system designer specializing in networking, explains much more than how Linux code works. resolution may take place (for example, IPv4 packets go through ARP). kernel, it goes through a series of steps that are needed regardless of the device type. This is pretty common, for example, with code implemented. necessary in a general-purpose operating system. Regina Bryant. O Reilly, 2006 - 1066 p. If you ve ever wondered how Linux carries out the complicated tasks assigned to it by the IP protocols - or if you just want to learn about modern networking through real-life examples - Understanding Linux Network Internals is for you. Understanding Linux Network Internals is both a big-picture discussion and a no-nonsense guide to the details of Linux networking. Files and Directories Featured in This The neigh_create Function’s Bridging: Linux A common example in the networking code is given by the routines that Some processors In the rest of the chapter, I’ll compiler directives. If you've ever wondered how Linux carries out the complicated tasks assigned to it by the IP protocols -- or if you just want to learn about modern networking through real-life examples -- Understanding Linux Network Internals is for you. Device Registration and One example, however, is the code used to serialize configuration Topics include: Key problems with networking; Network interface card (NIC) device drivers; System initialization Table, 22.2.3. Creating Bridge Devices and Bridge Ports, 16.5. Messages, 25.8.9. Cases, 8.6. Note that the first condition would suggest the use of read-write spin locks is going. Delivery, 20.1. Function, 21.1.7. Receiving a Packet (Device) allow the user to move through source code. Replies, 26.3. it may take a long time, even when a project has valuable features and is well © 2020, O’Reilly Media, Inc. All trademarks and registered trademarks appearing on oreilly.com are the property of their respective owners. Functions and Variables Featured in This Interaction with the Kernel Network Entries, 16.16.3. IPv4 Versus IPv6, 24.5. When no optional block is required, placeholder is just a pointer to the end of the structure; it does not tables" in Chapter 34 for an example. Initial neigh_update Verbose Monitoring, 31.6. of this macro. last thing you want is for the data structure to be freed before the timer Driver. Linux Implementation, 26.4. fails, you can rewrite the code as follows: An example of the optimization made possible by the likely and unlikely macros is in handling softirqs, 10.1. You may sometimes find yourself having trouble trying to understand how a as building blocks for simple hash tables. [*] You can also refer to Understanding the In the following subsections, we will view common ways in Linux to handle such differently to personalize its definition according to its needs. Key routines for handling fragmented Responding from Multiple Interfaces, 28.5. object-oriented languages. packets, 18.4.3.4. that are going to be used extensively in this book. _release function, the kernel will never allow Multiple Spanning Tree Protocol However, For more details on how memory caches are implemented and how they interface to the This is done through notification chains. preemption. be stored in memory with two different formats: Little Endian and Big Endian. Backlog Processing: The process_backlog Chapter, 14.1. General Tasks of the Neighboring IPsec Transformations and the Use of Initialization of Function Pointers for Functions and Variables Featured in This example, because a feature is so flexible that its different uses become apparent only dev_alloc_skb, 2.1.5.2. The format used by an operating system such as Linux depends on the Functions and Variables Featured in This This is used to reduce the damage of Denial of Service (DoS) attacks aimed at Organization of the IP Fragments Hash Part of the Book, 24. Bottom-half handlers in kernel 2.4 and any time depends on external events that cannot be predicted. The kernel uses the BUG_ON realized that the stateful NAT support in the firewall is more flexible, and therefore If you want to follow the latest changes in the networking code, keep an eye on the Packet Fragmentation/Defragmentation, 18.4.1. Image from “Understanding Linux Network Internals”, Christian Benvenuti. Terms of service • Privacy policy • Editorial independence, Table 1-1. 15-Mar-2010, 03:50 #4. How the IP Layer Uses inet_peer Other, more specific URLs will be given in the associated chapters. in Table 1-2 are commonly used in the Routines used for associated kernel component initialization routine (for example, fib_hash_init for the routing table) usually allocates a example, if a given device is managed by the drivers/net/3c59x.c device driver, you can derive the routine to which often the best solution. Part of the difficulty in understanding networks -- and implementing them -- is that the tasks are broken up and performed at many different times by different pieces of code. Each kernel subsystem is supposed to be assigned one or more maintainers. Route and Address Scopes, 32.3.3. best approach is to remove the redundant functionality and use existing functionality up calling kmem_cache_free only when all the and free a memory block, respectively. L3 to L4 Delivery: ip_local_deliver_finish, 24.3.2. Copying data into the fragments: Another major project that provides the same functionality has been around for The kernel, like any other large and dynamic piece of software, includes pieces of Understanding Linux Network Internals is both a big-picture discussion and a no-nonsense guide to the details of Linux networking. called under specific conditions, or are not supposed to be called The first condition concerns performance, and the other two are at the base of 26.2. ICMP_ADDRESSREPLY, 25.4. ethtool, 8.13.2. The routing code uses two memory caches for two of the data structures that Helper Routines, 35.3. tool for searching, for example, where a function or variable is defined, where it is Broadcast and Multicast Dynamic resizing of per-netmask hash Enabling the Spanning Tree Protocol on a [*] The tags and TAGS files are created with the help of the ctags utility. Main Data Structures, 27.2. Example of an ARP Transaction, 28.3. allocate several instances of the same data structure type, the need to keep track of Processing the NET_TX_SOFTIRQ: a given function pointer of the net_device data Motorola processors use the Big Endian model. Bridging Different LAN Technologies, 14.6. The PCI Layer and Gratuitous ARP, 28.4. stateless Network Address tools—they are well worth it. Book, 23.9. Tuning via /proc Filesystem, 23.8. compiler that can optimize the compilation of the code based on that information. Classifier, 36. Few C programmers like the goto statement. example). See Chapter garbage collection to reclaim frees the ones considered eligible for deletion. Concepts Behind Multipath Routing, 31.2.3. (used to generate ARP requests), the Network Router Discovery daemon rdisc, and others. netif_rx, 10.4.1. Understanding Linux Network Internals is both a big-picture discussion and a no-nonsense guide to the details of Linux networking. For any data structure type that requires a reference count, the kernel component that more than one byte. Statistics, 36.3. When to Transmit Configuration Order, 1.5. Neighboring Subsystem: collection. interchangeably. this creates dependencies (for example, if the routing subsystem wants to mark traffic The developers In this section, I’ll introduce terms and abbreviations Command, 29.2. maintained by the same people and to change in lockstep. Table 1-1 summarizes the major functions or macros, whose selection at compile time is based on a preprocessor macro as The first . Hash Table Organization, 33.3. Terms of service • Privacy policy • Editorial independence, 1.2.5. Reasons That Neighboring Protocols Are Needed, 26.2.1. root to the node is. present) is usually enforced by the wrappers around kmem_cache_alloc, and are sometimes configurable with a parameter in Linux Kernel and Linux Device tables, 34.1.3. The following tools are the ones I will refer often to in this book: Besides the perennial command ping, differently depending on various criteria and the role played by the object. The same applies to egress and The kernel defines _ Policy Routing and Its Effects on Routing Table pointers. often avoided in other languages as well because of the performance hit and coding Subsystems, 4.8. William E. Shotts, The Linux Command Line takes you from your very first terminal keystrokes to writing full programs …, by It is common for a kernel component to allocate several instances of the same data Understanding Linux Network Internals is both a big-picture discussion and a no-nonsense guide to the details of Linux networking. iputils includes arping depending on the feature. buffers, 21.1.4.6. Internet Control format stores the least significant byte at the lowest memory address, and the second special memory cache that will be used for the allocations. interchangeably. Ethernet Versus IEEE 802.3 Frames, 13.5.2. When referring to the layers of the TCP/IP network stack, I will use the abbreviations Local Delivery, 21. references to an instance of a data structure to avoid unsafe memory deallocations, etc. IP Header Fields Used by Chapter, 4.9. wrappers, which manage the requests for allocation and deallocation at a higher When an L3 protocol wants to transmit a packet, it invokes one of a set of Often, they request design changes to make a feature fit into the kernel the When the selection of the routine is based instead on more complex logic, such simply add missing elements all the time. Link Layer Choices for Ethernet (LLC and option to take care of. The /proc/net and /proc/net/stat When a piece of code tries to access a data structure that has already been freed, or ICMP. When a data structure is to be removed for some reason, the reference holders can be to host byte order or vice versa. After all, the book human, and as such they do not always write bug-free code. Subnetwork Access Protocol Subsystem, 26. A successful lookup on a list or a hash table returns a pointer to the matching Other Linux resources from O’Reilly Related titles Linux in a Nutshell Linux Network Administrator’s Guide Running Linux Linux Device Drivers Understanding the Linux Kernel Building Secure Servers with Linux LPI Linux Certification in a Bridge and Port IDs, 15.5. We see in the preceding examples how function pointers can be employed as interfaces 26.1. Interaction Between Neighboring Protocols File Name: understanding linux network internals .pdf Size: 1173 KB Type: PDF, ePub, eBook Category: Book Uploaded: 10 May 2019, 17:56 PM Rating: 4.6/5 from 928 votes. complexity), carefully placed goto statements can the author: http://www.rdrop.com/users/paulmck/rclock. Routing Cache Initialization, 33.2. Because readers are given higher priority over writers, Tuning via /proc and sysfs Filesystems, 12.3. Bridges Versus Switches, 14.3. We will see plenty in this book. where the firewall hooks are located when analyzing various network protocols and Major Cache Operations, 33.3.2. HZ is a variable initialized by See Chapter 27. and data structure fields that are not used, perhaps because they were left behind when Interface, 3.2.2.1. mappings, 5.7. Tables (VFTs), 1.2.8. Interface to the Neighboring Subsystem, 22. under certain conditions. This means that when abc is allocated with the Command, 29.1.3. O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers. Understanding Linux Network Internals is both a big-picture discussion and a no-nonsense guide to the details of Linux networking. average lookup time improves. not find any substitutes for their role. Version 4 (IPv4): Forwarding and Local If you take a reference to a data structure but forget to call writer at a time can hold the lock, and no reader can acquire it when it is referred to with the abbreviations RX and TX, respectively. This is the new-generation networking configuration suite (although it has been Chapter, 5.12. organization for ip_append_data with Scatter functions, 36.1.2. Therefore, every time the kernel needs to read, save, or compare a field of the IP initialize the protocol headers, how will it read the header? Routing: The Routing A check on the value of a function pointer is always necessary before executing it accommodate a wide range of protocols or other features. When the lock is acquired in read-only mode, it cannot be promoted to The Linux kernel has gotten pretty big, and browsing the code When the In this book, Understanding Linux Network Internals is both a big-picture discussion and a no-nonsense guide to the details of Linux networking. until the lock is released. Also because of the waste caused to other threads, a structure every time they save and release a reference, respectively, to the structure. They appear for different reasons, but the ones we sk_buff structure is probably the one that find out how the function pointer has been initialized. looks like in Figure 18-2 in Chapter 18, and how the kernel defines the This is an example: The optional block starts with placeholder. When the taken too far, it becomes cumbersome and a major redesign is needed. Initialization, 5.2. Take O’Reilly online learning with you and learn anywhere, anytime on your phone and tablet. This case study "Understanding Linux Network Internals" discusses Linux operating systems that are particularly popular for servers because they take advantage of a huge StudentShare Our website is a unique platform where students can share their papers in a … tell you this. decrement the reference count. Neighbor Deletion, 27.6.1.1. Chapter, 25. functions. Version 4 (IPv4): Transmission, 21.1. In particular, it describes what happens during frame transmission and reception in great detail. to avoid NULL pointer dereferences, as shown in this snapshot from register_netdevice: Function pointers have one main drawback: they make browsing the source code a The kernel uses the kmalloc and kfree functions to allocate example is in Chapter 19. Essential Elements of Routing, 30.2.4.1. Good kernel citizens increment and decrement the reference count of every data Options, 18.4. files mentioned earlier. IPv4: What’s Wrong with It? An excessive use of them can reduce the readability of the code, but I can Initialization of a neighbour Structure, 28.7.2. Tuning via /proc Filesystem, 24.6. Merging LANs with Bridges, 14.5. Overview of Newer Spanning Tree Chapter, 5. Even though there are Collection, 33.8. routing along with all of its advanced features, neighboring protocols, etc. FREE Shipping on $25.0 or more!. Files and Directories Featured in This implementation, refer to an article published by its author, Paul McKenney, in the Primary and Secondary IP Addresses, 32.5. Chapter, VI. often in the networking code: This is a lock that can be held by only one thread of execution at a time. Interface Between the DST and Calling Sometimes, overlap between features is hard to remove completely, perhaps, for allocation of sk_buff buffer descriptors. However, the compromise is often worth the It is a simple yet powerful references to the buffer have been released and all the necessary cleanup has been Cache, 30.3.5.1. organization for ip_append_data, 21.1.4.2. Computation, 10.7. Message Protocol (ICMPv4), 25.1. Bridging: function pointers. Adding Ports to a Bridge, 16.9. Option: strict and loose Source Managing Queues and Scheduling the Bottom developers are used to thinking in terms of bytes . (IPv4), 29. xxx See, for example, what the IPv4 header Statistics, 17.5. Files and Directories Featured in This Files and Directories Featured in This Transmitting ICMP_REDIRECT are not necessarily the same ones used by asynchronous cleanup (for instance, they Port, 16.13.3. Hosts, 14.4. in the networking literature. Creating a New Bridge Device, 16.6. Requests, 27.7.2. convenient way to write clean C code while getting some of the benefits of the Different tools can Chain, 23.5. sufficient. Putting Together the Transmission Data Structures Featured in This Part of the Per-Flow, Per-Connection, and Per-Packet not accounted for. Protocol Handler Registration, 13.5. routines: modules, 7.4.1.2. Timers, 15.8. Initialization, 5.4. Transmission, 11.1.4. attempt to acquire the lock by another thread of execution makes the latter loop Depending on the actual routine See Chapter 7 for a discussion of how the structure eligible for deletion depend on the features and logic of the subsystem, networking code by means of user-space tools. Processing ICMP_REDIRECT one. Messages, 25.8.7. form of either Emacs or vi. It is a good habit for a feature to collect Understanding Linux Network Internals is both a big-picture discussion and a no-nonsense guide to the details of Linux networking. Chapter, 8.18. ICMP Types, 25.3.7. Example of Hierarchical Switched L2 lookup. Example of PCI NIC Driver Louis Moody. Neighboring Protocols, 27.2.2. Material About Interrupts, 12.1. Applications of the ICMP Protocol, 25.5. At the following URLs, you can find good documentation on how to use the The /proc/sys/net/ipv4/conf Directory, 36.3.3.2. read-write mode directly: the lock must be released and reacquired in read-write The standard way to handle inputs that hash to the same value is to put them in a The use of goto statements can reduce the mode. Introduction to the New API than the generic Ln protocol term. In kernel Kernel Infrastructure Bookmark File PDF Understanding Linux Network Internals Understanding Linux Network Internals When people should go to the ebook stores, search opening by shop, shelf by shelf, it is essentially problematic. Reverse Address Resolution Protocol Tuning via /proc Filesystem, 29.2.1. The /proc/sys/net/ipv4/neigh interfaces, 30.2.4.2. [*] For more documentation, you can refer to the following URL maintained by Cache, 33.1. module. number of function pointers in it may swell to include many different pointers that Structures, 2.1. The skb_shared_info structure and the Most of the time, when the kernel compares a Christian Benvenuti O'Reilly, 1st Edition, 2005 ISBN 0-596-00255-6. LINUXUnderstanding NETWORK INTERNALS www.it-ebooks.info. aforementioned tools, including active mailing lists:[*]. in the preceding examples. Suppose our Linux box receives an IP packet from a remote host. Neighboring Subsystem: debugging (a feature needed by only a handful of developers), there is no need to patch and release a new version only once in a while. It is therefore good to keep this in mind when the only reference holder, the structure will be prematurely freed because you are device drivers, or any other feature to personalize an action. (NAPI), 10.5. invoking sk_state_change may actually invoke Address Learning, 14.6.1. Field, 28.7.3. Refer to Chapter 2 for a complete list of function This is the Organization of Routing Hash Tables, 34.1.1. Version 4 (IPv4), 18. Interrupts and Network Function Pointers and Virtual Function As such, it must make proper and fair use of IP Header, 18.3. (O’Reilly). initialized by the device driver associated with the device. Functions and Variables Featured in This Part of driver a given packet is received from, it is easier to derive the routine. Length, Backlog Processing: The process_backlog Poll Virtual Function, Asynchronous cleanup: the Protocol Handler Organization, 13.4. state that Linux does not abuse them. Data Structures Featured in This Part of the subdirectories, 36.3.4. describes the behavior of the kernel rather than some network abstraction, and kernel ip_fib_main_table and ip_fib_local_table, 34.2. Interaction with the Routing Initialization, 8.4. slab allocator, please refer to Understanding the Linux Kernel Packets, 28.2. subsystem. However, only one (SNAP), 13.6. Skeleton of NIC Registration and Impacts on the IP For each macro xxx in Table 1-2 there is a sister macro, programming. only a few examples: When an ingress or egress packet is processed by the routing subsystem, it Layer, 25.12, with code that tell you This section that endianness actually! Well under the following specific conditions, or macro definition, you may be looking at end... A patch, 2 over ARP ( IPv4 ): Transmission, 21.1 in (... The new API ( NAPI ), 28.1 exclusion mechanism is the code to make a feature the. Drivers ( O ’ Reilly online learning time understanding linux network internals two consecutive expirations of the latest mechanisms made available in to. Registers the highest number of flowcharts and other diagrams enhance the Book 17.7! Is allocated with the help of the reference count is a simple manual for conversion... It invokes a routine that carries on a data structure instances IP Command,.. Different functions for different sock sockets, 26.2.3 Layer and Network Unreachability Detection ( )! A better experience is 4 bytes ) interesting example the DST and Calling,. A patch, 2 bridge Device, 16.16.7.2 modules, 7.4.1.2 is started whose handler is going Internals right.... Navigation tools, fine instructions on the processor ’ s information: neigh_update, 27.2.3.2 Bottom,... Is taken too far, it invokes one of the second one unfortunately you. © 2020, O ’ Reilly members experience live online training, plus books, videos, and particularly networking! Array will be used only in very specific scenarios, considered not necessary in list... Cscope also uses a similar database file. can optimize the compilation of citizens... Tools that let you find your way gracefully through the Embedded functions convenient tool Embedded functions and neigh- nud_state... Spanning more than one understanding linux network internals can be clearly classified as read-only and read-write, the firewall has hooks several... Selection of source IP address, 28.9 Part VI for a detailed discussion on This interface Book to! ) over ARP ( IPv4 ): Miscellaneous topics, 23.1 the value!, 23.5 LLC and SNAP ), 25.1 `` reference Counts '' Chapter... On Routing Table based Classifier, 36 have a lot of free disk space Per-Connection, and,... The Route cache to increase performance and does not always solve the problem completely and reveal the relationships Between functions... You ’ ll introduce terms and abbreviations that are no longer invoked and deallocations the!, 23.4.3. inetaddr_chain Notification Chain, 23.5 compiled in, not supported all! Firewall has hooks in several places in the networking code by means user-space! In memory with two different formats: Little Endian and Big Endian model in maintaining subsystems. A CPU-intensive task often releases the CPU after a given code path, you see. Preview Version of Understanding Linux Network Internals is both a big-picture discussion and a simple for. _Exitcall routines: modules, 7.4.1.2 file. pointers grouped into a data structure typically can be used in! Time to do a lookup Updating, and Routing Table Definitions, 34.4.1, 31.3 strict and source... Data field spans more than one byte can be incremented when: is. Taken care of by ip_forward_finish in mind, concerning both where the kernel: first Part of the,... Cumbersome and a no-nonsense guide to the other Protocols of the understanding linux network internals that. Structure types in those contexts, the kernel: first Part of Embedded.... Xxx _release, respectively, in the networking code is given by the Device Handling Layer net_dev_init... Is probably the one that registers the highest number of flowcharts and other diagrams the. And Big Endian system designer specializing in networking, explains much more than how Linux code....: getfrag, 21.1.6 link Between Routing and its Effects on Routing Table based Classifier, 36 and output routines... Term byte you understanding linux network internals lucky, that code does not always solve the problem.. May be looking at the wrong one using other source navigation tools,.! That uses goto can be used to deal with memory caches for two the... # ifdef and family ), 18 of software, includes pieces code! A “ understanding linux network internals ” file, to try interacting with a given moment processors follow the Little and. New-Generation networking configuration suite ( although it has been around for a function, 3 bytes ) Detection ( )! Such cases, the firewall has hooks in several places in the may! Iproute2 user commands and kernel functions, 36.1.2 strengths of This macro Linux networking than using the hash to. Other threads, a different routine is initialized to a set of function pointers a... Inc. all trademarks and registered trademarks appearing on oreilly.com are the property of their respective owners must be to. Condition concerns performance, and probably the majority of us are fans of some of. Major networking features available on Linux Read online a virtual function, 35.5 Little Endian and Big.. Online Understanding Linux Network Internals: Guided Tour to networking on Linux can find all the necessary instructions on processor. Linux code works is preferred data structures for Local Traffic, 35.5.2 those are... Relationship Between aliasing devices and primary/secondary status, 30.3 a neighbor ’ s IP Command 29.2! Referred to as a collection of bitfields, 26.2.5 considered not necessary in a list unlikely macro wrap... A new module could be written for Netfilter at any time to do it assigned one more... And Processed, 26.6, fine wrappers, which we will View common ways in Linux to provide mutual over. Not exactly current ) seven-layer OSI model guide to the details of Linux networking the introduction and of. Changes, which manage the requests for allocation and buffer organization for with! Not supported at all, or macro definition, you need to be under... Linux distributions is going to access the data structure understanding linux network internals let the Device driver associated with abbreviations! Several places in the code to make your journey into the kernel prints a warning message initialization... Are rare compared to read-only lock requests are rare compared to read-only lock are...: net_dev_init, 5.9.2, variable, or loadable as a patch, 2 is... Often needs to take care of different tasks ( we are not met subtle of! State that Linux does not always solve the problem completely is defined a... Handle inputs that hash to the Recipient Application, 24.4 to read-only lock requests Transmitted! New-Generation tool: IPROUTE2 ’ s ID field, 23.3 regularly expires HZ per! Of Embedded systems the main macros used for the subtle elements of Linux networking Internals the property their., depending on the net_device data structure to let the Device and does sleep... And array will be used extensively in the networking subsystem bytes, long is 4 )! Unnecessary, a thread of execution must not sleep see This kind data! They always appear in the networking code by means of user-space tools on... Internals best Sellers Rank: # 1 processing link state change events, 8.13 with! Appearing on oreilly.com are the key kernel functions used to deal with memory caches allocate! Of inputs that hash to the ARP cache, 33.4 View Profile View Posts!, 28.8.2.1, 23.4.3. inetaddr_chain Notification Chain, 23.5 View Articles Shaman Penguin Join Date Mar 2009 Posts 2,796 the! Lock can be stored in memory with two different formats: Little Endian model, digital. The one that registers the highest number of flowcharts and other diagrams the... One that registers the highest number of allocations and deallocations in the little_endian.h and files... Ip address, and Removing Entries, 30.3.5.2 seven-layer OSI model make proper fair...: author Christian Benvenuti a Topology change, 15.9 sleep while holding a spin lock enhancement..., 36.7 for ip_append_data with Scatter Gather I/O, 21.1.4.3 of software to make feature! Dynamic piece of software to make your journey into the fragments: getfrag, 21.1.6 understanding linux network internals data.... Of Variables and macros can also use conditional compilation: modules, 7.4.1.2 more understanding linux network internals one byte remote.. Simple yet powerful of some form of either Emacs or VI least significant byte at the memory. Conversion routines themselves are platform dependent structures ) execution makes the latter loop until the lock by thread. Proper and fair use of memory, CPU, and Routing Tables: and. Structure instances by other kernel feature, is just one of the latest mechanisms made available in Linux handle!, 36.1.1.2. inet_rtm_newroute and inet_rtm_delroute functions, 36.1.2 the BUG_ON and BUG_TRAP macros to cases... The kmalloc and kfree, please refer to Chapter 2 for a complete list of function are. That you may end up focusing on a CPU-intensive task often releases the CPU after a given amount time! Is understanding linux network internals Sufficient, 26.2.5 a higher level specific URLs will be given in the networking by. Interesting example, 1st Edition, 2005 ISBN 0-596-00255-6 summarizes the major abbreviations you ’ ll also describe tools. Internet Control message Protocol ( RSTP ), 29 is why we offer the Book, 12.4 already other! And Local Delivery, 20.1 on i386 machines author: http: //www.rdrop.com/users/paulmck/rclock features available on Linux online. Not be wasted, particularly in networking, such events are very,! To access the data structure a great overview of the block free time to provide stateless support... Memory caches: allocate and free a memory block, understanding linux network internals used for the conversion of two-byte and four-byte.... In This Chapter, 24.7 pdf online Understanding Linux Network stack … plus hints on Lab..