34 skills found · Page 1 of 2
RevenantX / LiteNetLibLite reliable UDP library for Mono and .NET
PowerBroker2 / SerialTransferArduino library to transfer dynamic, packetized data fast and reliably via Serial, I2C, etc.
ccie18643 / PyTCPPyTCP is a fully functional TCP/IP stack written in Python. It supports TCP stream-based transport with reliable packet delivery based on a sliding window mechanism and basic congestion control. It also supports IPv6/ICMPv6 protocols with SLAAC address configuration. It operates as a user space program attached to the Linux TAP interface.
nyxpsi / NyxpsiWIP: Next-gen network protocol for reliable data transfer in lossy environments. Outperforms TCP/UDP in high packet loss scenarios.
PowerBroker2 / PySerialTransferPython package to transfer data in a fast, reliable, and packetized form
ctran / TinyRadiusTinyRadius is a small, fast and reliable Java Radius library capable ofsending and receiving Radius packets as specified by RFC 2865/2866.
Saishy / TinyBirdNet Unity[DISCONTINUED] A high level API for making networked games in Unity, utilizes https://github.com/RevenantX/LiteNetLib
bookworm52 / EthicalHackingFromScratchWelcome to my comprehensive course on python programming and ethical hacking. The course assumes you have NO prior knowledge in any of these topics, and by the end of it you'll be at a high intermediate level being able to combine both of these skills to write python programs to hack into computer systems exactly the same way that black hat hackers do. That's not all, you'll also be able to use the programming skills you learn to write any program even if it has nothing to do with hacking. This course is highly practical but it won't neglect the theory, we'll start with basics of ethical hacking and python programming and installing the needed software. Then we'll dive and start programming straight away. You'll learn everything by example, by writing useful hacking programs, no boring dry programming lectures. The course is divided into a number of sections, each aims to achieve a specific goal, the goal is usually to hack into a certain system! We'll start by learning how this system work and its weaknesses, then you'll lean how to write a python program to exploit these weaknesses and hack the system. As we write the program I will teach you python programming from scratch covering one topic at a time. By the end of the course you're going to have a number of ethical hacking programs written by yourself (see below) from backdoors, keyloggers, credential harvesters, network hacking tools, website hacking tools and the list goes on. You'll also have a deep understanding on how computer systems work, how to model problems, design an algorithm to solve problems and implement the solution using python. As mentioned in this course you will learn both ethical hacking and programming at the same time, here are some of the topics that will be covered in the course: Programming topics: Writing programs for python 2 and 3. Using modules and libraries. Variables, types ...etc. Handling user input. Reading and writing files. Functions. Loops. Data structures. Regex. Desiccation making. Recursion. Threading. Object oriented programming. Packet manipulation using scapy. Netfilterqueue. Socket programming. String manipulation. Exceptions. Serialisation. Compiling programs to binary executables. Sending & receiving HTTP requests. Parsing HTML. + more! Hacking topics: Basics of network hacking / penetration testing. Changing MAC address & bypassing filtering. Network mapping. ARP Spoofing - redirect the flow of packets in a network. DNS Spoofing - redirect requests from one website to another. Spying on any client connected to the network - see usernames, passwords, visited urls ....etc. Inject code in pages loaded by any computer connected to the same network. Replace files on the fly as they get downloaded by any computer on the same network. Detect ARP spoofing attacks. Bypass HTTPS. Create malware for Windows, OS X and Linux. Create trojans for Windows, OS X and Linux. Hack Windows, OS X and Linux using custom backdoor. Bypass Anti-Virus programs. Use fake login prompt to steal credentials. Display fake updates. Use own keylogger to spy on everything typed on a Windows & Linux. Learn the basics of website hacking / penetration testing. Discover subdomains. Discover hidden files and directories in a website. Run wordlist attacks to guess login information. Discover and exploit XSS vulnerabilities. Discover weaknesses in websites using own vulnerability scanner. Programs you'll build in this course: You'll learn all the above by implementing the following hacking programs mac_changer - changes MAC Address to anything we want. network_scanner - scans network and discovers the IP and MAC address of all connected clients. arp_spoofer - runs an arp spoofing attack to redirect the flow of packets in the network allowing us to intercept data. packet_sniffer - filters intercepted data and shows usernames, passwords, visited links ....etc dns_spoofer - redirects DNS requests, eg: redirects requests to from one domain to another. file_interceptor - replaces intercepted files with any file we want. code_injector - injects code in intercepted HTML pages. arpspoof_detector - detects ARP spoofing attacks. execute_command payload - executes a system command on the computer it gets executed on. execute_and_report payload - executes a system command and reports result via email. download_and_execute payload - downloads a file and executes it on target system. download_execute_and_report payload - downloads a file, executes it, and reports result by email. reverse_backdoor - gives remote control over the system it gets executed on, allows us to Access file system. Execute system commands. Download & upload files keylogger - records key-strikes and sends them to us by email. crawler - discovers hidden paths on a target website. discover_subdomains - discovers subdomains on target website. spider - maps the whole target website and discovers all files, directories and links. guess_login - runs a wordlist attack to guess login information. vulnerability_scanner - scans a target website for weaknesses and produces a report with all findings. As you build the above you'll learn: Setting up a penetration testing lab to practice hacking safely. Installing Kali Linux and Windows as virtual machines inside ANY operating system. Linux Basics. Linux terminal basics. How networks work. How clients communicate in a network. Address Resolution Protocol - ARP. Network layers. Domain Name System - DNS. Hypertext Transfer Protocol - HTTP. HTTPS. How anti-virus programs work. Sockets. Connecting devices over TCP. Transferring data over TCP. How website work. GET & POST requests. And more! By the end of the course you're going to have programming skills to write any program even if it has nothing to do with hacking, but you'll learn programming by programming hacking tools! With this course you'll get 24/7 support, so if you have any questions you can post them in the Q&A section and we'll respond to you within 15 hours. Notes: This course is created for educational purposes only and all the attacks are launched in my own lab or against devices that I have permission to test. This course is totally a product of Zaid Sabih & zSecurity, no other organisation is associated with it or a certification exam. Although, you will receive a Course Completion Certification from Udemy, apart from that NO OTHER ORGANISATION IS INVOLVED. What you’ll learn 170+ videos on Python programming & ethical hacking Install hacking lab & needed software (on Windows, OS X and Linux) Learn 2 topics at the same time - Python programming & Ethical Hacking Start from 0 up to a high-intermediate level Write over 20 ethical hacking and security programs Learn by example, by writing exciting programs Model problems, design solutions & implement them using Python Write programs in Python 2 and 3 Write cross platform programs that work on Windows, OS X & Linux Have a deep understanding on how computer systems work Have a strong base & use the skills learned to write any program even if its not related to hacking Understand what is Hacking, what is Programming, and why are they related Design a testing lab to practice hacking & programming safely Interact & use Linux terminal Understand what MAC address is & how to change it Write a python program to change MAC address Use Python modules and libraries Understand Object Oriented Programming Write object oriented programs Model & design extendable programs Write a program to discover devices connected to the same network Read, analyse & manipulate network packets Understand & interact with different network layers such as ARP, DNS, HTTP ....etc Write a program to redirect the flow of packets in a network (arp spoofer) Write a packet sniffer to filter interesting data such as usernames and passwords Write a program to redirect DNS requests (DNS Spoofer) Intercept and modify network packets on the fly Write a program to replace downloads requested by any computer on the network Analyse & modify HTTP requests and responses Inject code in HTML pages loaded by any computer on the same network Downgrade HTTPS to HTTP Write a program to detect ARP Spoofing attacks Write payloads to download a file, execute command, download & execute, download execute & report .....etc Use sockets to send data over TCP Send data reliably over TCP Write client-server programs Write a backdoor that works on Windows, OS X and Linux Implement cool features in the backdoor such as file system access, upload and download files and persistence Write a remote keylogger that can register all keystrikes and send them by Email Interact with files using python (read, write & modify) Convert python programs to binary executables that work on Windows, OS X and Linux Convert malware to torjans that work and function like other file types like an image or a PDF Bypass Anti-Virus Programs Understand how websites work, the technologies used and how to test them for weaknesses Send requests towebsites and analyse responses Write a program that can discover hidden paths in a website Write a program that can map a website and discover all links, subdomains, files and directories Extract and submit forms from python Run dictionary attacks and guess login information on login pages Analyse HTML using Python Interact with websites using Python Write a program that can discover vulnerabilities in websites Are there any course requirements or prerequisites? Basic IT knowledge No Linux, programming or hacking knowledge required. Computer with a minimum of 4GB ram/memory Operating System: Windows / OS X / Linux Who this course is for: Anybody interested in learning Python programming Anybody interested in learning ethical hacking / penetration testing Instructor User photo Zaid Sabih Ethical Hacker, Computer Scientist & CEO of zSecurity My name is Zaid Al-Quraishi, I am an ethical hacker, a computer scientist, and the founder and CEO of zSecurity. I just love hacking and breaking the rules, but don’t get me wrong as I said I am an ethical hacker. I have tremendous experience in ethical hacking, I started making video tutorials back in 2009 in an ethical hacking community (iSecuri1ty), I also worked as a pentester for the same company. In 2013 I started teaching my first course live and online, this course received amazing feedback which motivated me to publish it on Udemy. This course became the most popular and the top paid course in Udemy for almost a year, this motivated me to make more courses, now I have a number of ethical hacking courses, each focusing on a specific field, dominating the ethical hacking topic on Udemy. Now I have more than 350,000 students on Udemy and other teaching platforms such as StackSocial, StackSkills and zSecurity. Instructor User photo z Security Leading provider of ethical hacking and cyber security training, zSecurity is a leading provider of ethical hacking and cyber security training, we teach hacking and security to help people become ethical hackers so they can test and secure systems from black-hat hackers. Becoming an ethical hacker is simple but not easy, there are many resources online but lots of them are wrong and outdated, not only that but it is hard to stay up to date even if you already have a background in cyber security. Our goal is to educate people and increase awareness by exposing methods used by real black-hat hackers and show how to secure systems from these hackers. Video course
BeRo1985 / RnlRNL - Realtime Network Library - The opensource reliable UDP network library
abhishekpatel-lpu / CICIDS 2017 Intrution Detection Intrusion Detection Systems (IDSs) and Intrusion Prevention Systems (IPSs) are the most important defense tools against the sophisticated and ever-growing network attacks. Due to the lack of reliable test and validation datasets, anomaly-based intrusion detection approaches are suffering from consistent and accurate performance evolutions. Our evaluations of the existing eleven datasets since 1998 show that most are out of date and unreliable. Some of these datasets suffer from the lack of traffic diversity and volumes, some do not cover the variety of known attacks, while others anonymize packet payload data, which cannot reflect the current trends. Some are also lacking feature set and metadata. CICIDS2017 dataset contains benign and the most up-to-date common attacks, which resembles the true real-world data (PCAPs). It also includes the results of the network traffic analysis using CICFlowMeter with labeled flows based on the time stamp, source, and destination IPs, source and destination ports, protocols and attack (CSV files). Also available is the extracted features definition. Generating realistic background traffic was our top priority in building this dataset. We have used our proposed B-Profile system (Sharafaldin, et al. 2016) to profile the abstract behavior of human interactions and generates naturalistic benign background traffic. For this dataset, we built the abstract behaviour of 25 users based on the HTTP, HTTPS, FTP, SSH, and email protocols. The data capturing period started at 9 a.m., Monday, July 3, 2017 and ended at 5 p.m. on Friday July 7, 2017, for a total of 5 days. Monday is the normal day and only includes the benign traffic. The implemented attacks include Brute Force FTP, Brute Force SSH, DoS, Heartbleed, Web Attack, Infiltration, Botnet and DDoS. They have been executed both morning and afternoon on Tuesday, Wednesday, Thursday and Friday.
AmirhosseinHonardoust / The Twin Test High Stakes MLA long-form article introducing the Twin Test: a practical standard for high-stakes machine learning where models must show nearest “twin” examples, neighborhood tightness, mixed-vs-homogeneous evidence, and “no reliable twins” abstention. Argues similarity and evidence packets beat probability scores for trust and safety.
SOYJUN / Implement ODR ProtocolOverview For this assignment you will be developing and implementing : An On-Demand shortest-hop Routing (ODR) protocol for networks of fixed but arbitrary and unknown connectivity, using PF_PACKET sockets. The implementation is based on (a simplified version of) the AODV algorithm. Time client and server applications that send requests and replies to each other across the network using ODR. An API you will implement using Unix domain datagram sockets enables applications to communicate with the ODR mechanism running locally at their nodes. I shall be discussing the assignment in class on Wednesday, October 29, and Monday, November 3. The following should prove useful reference material for the assignment : Sections 15.1, 15.2, 15.4 & 15.6, Chapter 15, on Unix domain datagram sockets. PF_PACKET(7) from the Linux manual pages. You might find these notes made by a past CSE 533 student useful. Also, the following link http://www.pdbuchan.com/rawsock/rawsock.html contains useful code samples that use PF_PACKET sockets (as well as other code samples that use raw IP sockets which you do not need for this assignment, though you will be using these types of sockets for Assignment 4). Charles E. Perkins & Elizabeth M. Royer. “Ad-hoc On-Demand Distance Vector Routing.” Proceedings of the 2nd IEEE Workshop on Mobile Computing Systems and Applications, New Orleans, Louisiana, February 1999, pp. 90 - 100. The VMware environment minix.cs.stonybrook.edu is a Linux box running VMware. A cluster of ten Linux virtual machines, called vm1 through vm10, on which you can gain access as root and run your code have been created on minix. See VMware Environment Hosts for further details. VMware instructions takes you to a page that explains how to use the system. The ten virtual machines have been configured into a small virtual intranet of Ethernet LANs whose topology is (in principle) unknown to you. There is a course account cse533 on node minix, with home directory /users/cse533. In there, you will find a subdirectory Stevens/unpv13e , exactly as you are used to having on the cs system. You should develop your source code and makefiles for handing in accordingly. You will be handing in your source code on the minix node. Note that you do not need to link against the socket library (-lsocket) in Linux. The same is true for -lnsl and -lresolv. For example, take a look at how the LIBS variable is defined for Solaris, in /home/courses/cse533/Stevens/unpv13e_solaris2.10/Make.defines (on compserv1, say) : LIBS = ../libunp.a -lresolv -lsocket -lnsl -lpthread But if you take a look at Make.defines on minix (/users/cse533/Stevens/unpv13e/Make.defines) you will find only: LIBS = ../libunp.a -lpthread The nodes vm1 , . . . . . , vm10 are all multihomed : each has two (or more) interfaces. The interface ‘eth0 ’ should be completely ignored and is not to be used for this assignment (because it shows all ten nodes as if belonging to the same single Ethernet 192.168.1.0/24, rather than to an intranet composed of several Ethernets). Note that vm1 , . . . . . , vm10 are virtual machines, not real ones. One implication of this is that you will not be able to find out what their (virtual) IP addresses are by using nslookup and such. To find out these IP addresses, you need to look at the file /etc/hosts on minix. More to the point, invoking gethostbyname for a given vm will return to you only the (primary) IP address associated with the interface eth0 of that vm (which is the interface you will not be using). It will not return to you any other IP address for the node. Similarly, gethostbyaddr will return the vm node name only if you give it the (primary) IP address associated with the interface eth0 for the node. It will return nothing if you give it any other IP address for the node, even though the address is perfectly valid. Because of this, and because it will ease your task to be able to use gethostbyname and gethostbyaddr in a straightforward way, we shall adopt the (primary) IP addresses associated with interfaces eth0 as the ‘canonical’ IP addresses for the nodes (more on this below). Time client and server A time server runs on each of the ten vm machines. The client code should also be available on each vm so that it can be evoked at any of them. Normally, time clients/servers exchange request/reply messages using the TCP/UDP socket API that, effectively, enables them to receive service (indirectly, via the transport layer) from the local IP mechanism running at their nodes. You are to implement an API using Unix domain sockets to access the local ODR service directly (somewhat similar, in effect, to the way that raw sockets permit an application to access IP directly). Use Unix domain SOCK_DGRAM, rather than SOCK_STREAM, sockets (see Figures 15.5 & 15.6, pp. 418 - 419). API You need to implement a msg_send function that will be called by clients/servers to send requests/replies. The parameters of the function consist of : int giving the socket descriptor for write char* giving the ‘canonical’ IP address for the destination node, in presentation format int giving the destination ‘port’ number char* giving message to be sent int flag if set, force a route rediscovery to the destination node even if a non-‘stale’ route already exists (see below) msg_send will format these parameters into a single char sequence which is written to the Unix domain socket that a client/server process creates. The sequence will be read by the local ODR from a Unix domain socket that the ODR process creates for itself. Recall that the ‘canonical’ IP address for a vm node is the (primary) IP address associated with the eth0 interface for the node. It is what will be returned to you by a call to gethostbyname. Similarly, we need a msg_recv function which will do a (blocking) read on the application domain socket and return with : int giving socket descriptor for read char* giving message received char* giving ‘canonical’ IP address for the source node of message, in presentation format int* giving source ‘port’ number This information is written as a single char sequence by the ODR process to the domain socket that it creates for itself. It is read by msg_recv from the domain socket the client/server process creates, decomposed into the three components above, and returned to the caller of msg_recv. Also see the section below entitled ODR and the API. Client When a client is evoked at a node, it creates a domain datagram socket. The client should bind its socket to a ‘temporary’ (i.e., not ‘well-known’) sun_path name obtained from a call to tmpnam() (cf. line 10, Figure 15.6, p. 419) so that multiple clients may run at the same node. Note that tmpnam() is actually highly deprecated. You should use the mkstemp() function instead - look up the online man pages on minix (‘man mkstemp’) for details. As you run client code again and again during the development stage, the temporary files created by the calls to tmpnam / mkstemp start to proliferate since these files are not automatically removed when the client code terminates. You need to explicitly remove the file created by the client evocation by issuing a call to unlink() or to remove() in your client code just before the client code exits. See the online man pages on minix (‘man unlink’, ‘man remove’) for details. The client then enters an infinite loop repeating the steps below. The client prompts the user to choose one of vm1 , . . . . . , vm10 as a server node. Client msg_sends a 1 or 2 byte message to server and prints out on stdout the message client at node vm i1 sending request to server at vm i2 (In general, throughout this assignment, “trace” messages such as the one above should give the vm names and not IP addresses of the nodes.) Client then blocks in msg_recv awaiting response. This attempt to read from the domain socket should be backed up by a timeout in case no response ever comes. I leave it up to you whether you ‘wrap’ the call to msg_recv in a timeout, or you implement the timeout inside msg_recv itself. When the client receives a response it prints out on stdout the message client at node vm i1 : received from vm i2 <timestamp> If, on the other hand, the client times out, it should print out the message client at node vm i1 : timeout on response from vm i2 The client then retransmits the message out, setting the flag parameter in msg_send to force a route rediscovery, and prints out an appropriate message on stdout. This is done only once, when a timeout for a given message to the server occurs for the first time. Client repeats steps 1. - 3. Server The server creates a domain datagram socket. The server socket is assumed to have a (node-local) ‘well-known’ sun_path name which it binds to. This ‘well-known’ sun_path name is designated by a (network-wide) ‘well-known’ ‘port’ value. The time client uses this ‘port’ value to communicate with the server. The server enters an infinite sequence of calls to msg_recv followed by msg_send, awaiting client requests and responding to them. When it responds to a client request, it prints out on stdout the message server at node vm i1 responding to request from vm i2 ODR The ODR process runs on each of the ten vm machines. It is evoked with a single command line argument which gives a “staleness” time parameter, in seconds. It uses get_hw_addrs (available to you on minix in ~cse533/Asgn3_code) to obtain the index, and associated (unicast) IP and Ethernet addresses for each of the node’s interfaces, except for the eth0 and lo (loopback) interfaces, which should be ignored. In the subdirectory ~cse533/Asgn3_code (/users/cse533/Asgn3_code) on minix I am providing you with two functions, get_hw_addrs and prhwaddrs. These are analogous to the get_ifi_info_plus and prifinfo_plus of Assignment 2. Like get_ifi_info_plus, get_hw_addrs uses ioctl. get_hw_addrs gets the (primary) IP address, alias IP addresses (if any), HW address, and interface name and index value for each of the node's interfaces (including the loopback interface lo). prhwaddrs prints that information out. You should modify and use these functions as needed. Note that if an interface has no HW address associated with it (this is, typically, the case for the loopback interface lo for example), then ioctl returns get_hw_addrs a HW address which is the equivalent of 00:00:00:00:00:00 . get_hw_addrs stores this in the appropriate field of its data structures as it would with any HW address returned by ioctl, but when prhwaddrs comes across such an address, it prints a blank line instead of its usual ‘HWaddr = xx:xx:xx:xx:xx:xx’. The ODR process creates one or more PF_PACKET sockets. You will need to try out PF_PACKET sockets for yourselves and familiarize yourselves with how they behave. If, when you read from the socket and provide a sockaddr_ll structure, the kernel returns to you the index of the interface on which the incoming frame was received, then one socket will be enough. Otherwise, somewhat in the manner of Assignment 2, you shall have to create a PF_PACKET socket for every interface of interest (which are all the interfaces of the node, excluding interfaces lo and eth0 ), and bind a socket to each interface. Furthermore, if the kernel also returns to you the source Ethernet address of the frame in the sockaddr_ll structure, then you can make do with SOCK_DGRAM type PF_PACKET sockets; otherwise you shall have to use SOCK_RAW type sockets (although I would prefer you to use SOCK_RAW type sockets anyway, even if it turns out you can make do with SOCK_DGRAM type). The socket(s) should have a protocol value (no larger than 0xffff so that it fits in two bytes; this value is given as a network-byte-order parameter in the call(s) to function socket) that identifies your ODR protocol. The <linux/if_ether.h> include file (i.e., the file /usr/include/linux/if_ether.h) contains protocol values defined for the standard protocols typically found on an Ethernet LAN, as well as other values such as ETH_P_ALL. You should set protocol to a value of your choice which is not a <linux/if_ether.h> value, but which is, hopefully, unique to yourself. Remember that you will all be running your code using the same root account on the vm1 , . . . . . , vm10 nodes. So if two of you happen to choose the same protocol value and happen to be running on the same vm node at the same time, your applications will receive each other’s frames. For that reason, try to choose a protocol value for the socket(s) that is likely to be unique to yourself (something based on your Stony Brook student ID number, for example). This value effectively becomes the protocol value for your implementation of ODR, as opposed to some other cse 533 student's implementation. Because your value of protocol is to be carried in the frame type field of the Ethernet frame header, the value chosen should be not less than 1536 (0x600) so that it is not misinterpreted as the length of an Ethernet 802.3 frame. Note from the man pages for packet(7) that frames are passed to and from the socket without any processing in the frame content by the device driver on the other side of the socket, except for calculating and tagging on the 4-byte CRC trailer for outgoing frames, and stripping that trailer before delivering incoming frames to the socket. Nevertheless, if you write a frame that is less than 60 bytes, the necessary padding is automatically added by the device driver so that the frame that is actually transmitted out is the minimum Ethernet size of 64 bytes. When reading from the socket, however, any such padding that was introduced into a short frame at the sending node to bring it up to the minimum frame size is not stripped off - it is included in what you receive from the socket (thus, the minimum number of bytes you receive should never be less than 60). Also, you will have to build the frame header for outgoing frames yourselves (assuming you use SOCK_RAW type sockets). Bear in mind that the field values in that header have to be in network order. The ODR process also creates a domain datagram socket for communication with application processes at the node, and binds the socket to a ‘well known’ sun_path name for the ODR service. Because it is dealing with fixed topologies, ODR is, by and large, considerably simpler than AODV. In particular, discovered routes are relatively stable and there is no need for all the paraphernalia that goes with the possibility of routes changing (such as maintenance of active nodes in the routing tables and timeout mechanisms; timeouts on reverse links; lifetime field in the RREP messages; etc.) Nor will we be implementing source_sequence_#s (in the RREQ messages), and dest_sequence_# (in RREQ and RREP messages). In reality, we should (though we will not, for the sake of simplicity, be doing so) implement some sort of sequence number mechanism, or some alternative mechanism such as split-horizon for example, if we are to avoid possible scenarios of routing loops in a “count to infinity” context (I shall explain this point in class). However, we want ODR to discover shortest-hop paths, and we want it to do so in a reasonably efficient manner. This necessitates having one or two aspects of its operations work in a different, possibly slightly more complicated, way than AODV does. ODR has several basic responsibilities : Build and maintain a routing table. For each destination in the table, the routing table structure should include, at a minimum, the next-hop node (in the form of the Ethernet address for that node) and outgoing interface index, the number of hops to the destination, and a timestamp of when the the routing table entry was made or last “reconfirmed” / updated. Note that a destination node in the table is to be identified only by its ‘canonical’ IP address, and not by any other IP addresses the node has. Generate a RREQ in response to a time client calling msg_send for a destination for which ODR has no route (or for which a route exists, but msg_send has the flag parameter set or the route has gone ‘stale’ – see below), and ‘flood’ the RREQ out on all the node’s interfaces (except for the interface it came in on and, of course, the interfaces eth0 and lo). Flooding is done using an Ethernet broadcast destination address (0xff:ff:ff:ff:ff:ff) in the outgoing frame header. Note that a copy of the broadcast packet is supposed to / might be looped back to the node that sends it (see p. 535 in the Stevens textbook). ODR will have to take care not to treat these copies as new incoming RREQs. Also note that ODR at the client node increments the broadcast_id every time it issues a new RREQ for any destination node. When a RREQ is received, ODR has to generate a RREP if it is at the destination node, or if it is at an intermediate node that happens to have a route (which is not ‘stale’ – see below) to the destination. Otherwise, it must propagate the RREQ by flooding it out on all the node’s interfaces (except the interface the RREQ arrived on). Note that as it processes received RREQs, ODR should enter the ‘reverse’ route back to the source node into its routing table, or update an existing entry back to the source node if the RREQ received shows a shorter-hop route, or a route with the same number of hops but going through a different neighbour. The timestamp associated with the table entry should be updated whenever an existing route is either “reconfirmed” or updated. Obviously, if the node is going to generate a RREP, updating an existing entry back to the source node with a more efficient route, or a same-hops route using a different neighbour, should be done before the RREP is generated. Unlike AODV, when an intermediate node receives a RREQ for which it generates a RREP, it should nevertheless continue to flood the RREQ it received if the RREQ pertains to a source node whose existence it has heretofore been unaware of, or the RREQ gives it a more efficient route than it knew of back to the source node (the reason for continuing to flood the RREQ is so that other nodes in the intranet also become aware of the existence of the source node or of the potentially more optimal reverse route to it, and update their tables accordingly). However, since an RREP for this RREQ is being sent by our node, we do not want other nodes who receive the RREQ propagated by our node, and who might be in a position to do so, to also send RREPs. So we need to introduce a field in the RREQ message, not present in the AODV specifications, which acts like a “RREP already sent” field. Our node sets this field before further propagating the RREQ and nodes receiving an RREQ with this field set do not send RREPs in response, even if they are in a position to do so. ODR may, of course, receive multiple, distinct instances of the same RREQ (the combination of source_addr and broadcast_id uniquely identifies the RREQ). Such RREQs should not be flooded out unless they have a lower hop count than instances of that RREQ that had previously been received. By the same token, if ODR is in a position to send out a RREP, and has already done so for this, now repeating, RREQ , it should not send out another RREP unless the RREQ shows a more efficient, previously unknown, reverse route back to the source node. In other words, ODR should not generate essentially duplicative RREPs, nor generate RREPs to instances of RREQs that reflect reverse routes to the source that are not more efficient than what we already have. Relay RREPs received back to the source node (this is done using the ‘reverse’ route entered into the routing table when the corresponding RREQ was processed). At the same time, a ‘forward’ path to the destination is entered into the routing table. ODR could receive multiple, distinct RREPs for the same RREQ. The ‘forward’ route entered in the routing table should be updated to reflect the shortest-hop route to the destination, and RREPs reflecting suboptimal routes should not be relayed back to the source. In general, maintaining a route and its associated timestamp in the table in response to RREPs received is done in the same manner described above for RREQs. Forward time client/server messages along the next hop. (The following is important – you will lose points if you do not implement it.) Note that such application payload messages (especially if they are the initial request from the client to the server, rather than the server response back to the client) can be like “free” RREPs, enabling nodes along the path from source (client) to destination (server) node to build a reverse path back to the client node whose existence they were heretofore unaware of (or, possibly, to update an existing route with a more optimal one). Before it forwards an application payload message along the next hop, ODR at an intermediate node (and also at the final destination node) should use the message to update its routing table in this way. Thus, calls to msg_send by time servers should never cause ODR at the server node to initiate RREQs, since the receipt of a time client request implies that a route back to the client node should now exist in the routing table. The only exception to this is if the server node has a staleness parameter of zero (see below). A routing table entry has associated with it a timestamp that gives the time the entry was made into the table. When a client at a node calls msg_send, and if an entry for the destination node already exists in the routing table, ODR first checks that the routing information is not ‘stale’. A stale routing table entry is one that is older than the value defined by the staleness parameter given as a command line argument to the ODR process when it is executed. ODR deletes stale entries (as well as non-stale entries when the flag parameter in msg_send is set) and initiates a route rediscovery by issuing a RREQ for the destination node. This will force periodic updating of the routing tables to take care of failed nodes along the current path, Ethernet addresses that might have changed, and so on. Similarly, as RREQs propagate through the intranet, existing stale table entries at intermediate nodes are deleted and new route discoveries propagated. As noted above when discussing the processing of RREQs and RREPs, the associated timestamp for an existing table entry is updated in response to having the route either “reconfirmed” or updated (this applies to both reverse routes, by virtue of RREQs received, and to forward routes, by virtue of RREPs). Finally, note that a staleness parameter of 0 essentially indicates that the discovered route will be used only once, when first discovered, and then discarded. Effectively, an ODR with staleness parameter 0 maintains no real routing table at all ; instead, it forces route discoveries at every step of its operation. As a practical matter, ODR should be run with staleness parameter values that are considerably larger than the longest RTT on the intranet, otherwise performance will degrade considerably (and collapse entirely as the parameter values approach 0). Nevertheless, for robustness, we need to implement a mechanism by which an intermediate node that receives a RREP or application payload message for forwarding and finds that its relevant routing table entry has since gone stale, can intiate a RREQ to rediscover the route it needs. RREQ, RREP, and time client/server request/response messages will all have to be carried as encapsulated ODR protocol messages that form the data payload of Ethernet frames. So we need to design the structure of ODR protocol messages. The format should contain a type field (0 for RREQ, 1 for RREP, 2 for application payload ). The remaining fields in an ODR message will depend on what type it is. The fields needed for (our simplified versions of AODV’s) RREQ and RREP should be fairly clear to you, but keep in mind that you need to introduce two extra fields: The “RREP already sent” bit or field in RREQ messages, as mentioned above. A “forced discovery” bit or field in both RREQ and RREP messages: When a client application forces route rediscovery, this bit should be set in the RREQ issued by the client node ODR. Intermediate nodes that are not the destination node but which do have a route to the destination node should not respond with RREPs to an RREQ which has the forced discovery field set. Instead, they should continue to flood the RREQ so that it eventually reaches the destination node which will then respond with an RREP. The intermediate nodes relaying such an RREQ must update their ‘reverse’ route back to the source node accordingly, even if the new route is less efficient (i.e., has more hops) than the one they currently have in their routing table. The destination node responds to the RREQ with an RREP in which this field is also set. Intermediate nodes that receive such a forced discovery RREP must update their ‘forward’ route to the destination node accordingly, even if the new route is less efficient (i.e., has more hops) than the one they currently have in their routing table. This behaviour will cause a forced discovery RREQ to be responded to only by the destination node itself and not any other node, and will cause intermediate nodes to update their routing tables to both source and destination nodes in accordance with the latest routing information received, to cover the possibility that older routes are no longer valid because nodes and/or links along their paths have gone down. A type 2, application payload, message needs to contain the following type of information : type = 2 ‘canonical’ IP address of source node ‘port’ number of source application process (This, of course, is not a real port number in the TCP/UDP sense, but simply a value that ODR at the source node uses to designate the sun_path name for the source application’s domain socket.) ‘canonical’ IP address of destination node ‘port’ number of destination application process (This is passed to ODR by the application process at the source node when it calls msg_send. Its designates the sun_path name for an application’s domain socket at the destination node.) hop count (This starts at 0 and is incremented by 1 at each hop so that ODR can make use of the message to update its routing table, as discussed above.) number of bytes in application message The fields above essentially constitute a ‘header’ for the ODR message. Note that fields which you choose to have carry numeric values (rather than ascii characters, for example) must be in network byte order. ODR-defined numeric-valued fields in type 0, RREQ, and type 1, RREP, messages must, of course, also be in network byte order. Also note that only the ‘canonical’ IP addresses are used for the source and destination nodes in the ODR header. The same has to be true in the headers for type 0, RREQ, and type 1, RREP, messages. The general rule is that ODR messages only carry ‘canonical’ IP node addresses. The last field in the type 2 ODR message is essentially the data payload of the message. application message given in the call to msg_send An ODR protocol message is encapsulated as the data payload of an Ethernet frame whose header it fills in as follows : source address = Ethernet address of outgoing interface of the current node where ODR is processing the message. destination address = Ethernet broadcast address for type 0 messages; Ethernet address of next hop node for type 1 & 2 messages. protocol field = protocol value for the ODR PF_PACKET socket(s). Last but not least, whenever ODR writes an Ethernet frame out through its socket, it prints out on stdout the message ODR at node vm i1 : sending frame hdr src vm i1 dest addr ODR msg type n src vm i2 dest vm i3 where addr is in presentation format (i.e., hexadecimal xx:xx:xx:xx:xx:xx) and gives the destination Ethernet address in the outgoing frame header. Other nodes in the message should be identified by their vm name. A message should be printed out for each packet sent out on a distinct interface. ODR and the API When the ODR process first starts, it must construct a table in which it enters all well-known ‘port’ numbers and their corresponding sun_path names. These will constitute permanent entries in the table. Thereafter, whenever it reads a message off its domain socket, it must obtain the sun_path name for the peer process socket and check whether that name is entered in the table. If not, it must select an ‘ephemeral’ ‘port’ value by which to designate the peer sun_path name and enter the pair < port value , sun_path name > into the table. Such entries cannot be permanent otherwise the table will grow unboundedly in time, with entries surviving for ever, beyond the peer processes’ demise. We must associate a time_to_live field with a non-permanent table entry, and purge the entry if nothing is heard from the peer for that amount of time. Every time a peer process for which a non-permanent table entry exists communicates with ODR, its time_to_live value should be reinitialized. Note that when ODR writes to a peer, it is possible for the write to fail because the peer does not exist : it could be a ‘well-known’ service that is not running, or we could be in the interval between a process with a non-permanent table entry terminating and the expiration of its time_to_live value. Notes A proper implementation of ODR would probably require that RREQ and RREP messages be backed up by some kind of timeout and retransmission mechanism since the network transmission environment is not reliable. This would considerably complicate the implementation (because at any given moment, a node could have multiple RREQs that it has flooded out, but for which it has still not received RREPs; the situation is further complicated by the fact that not all intermediate nodes receiving and relaying RREQs necessarily lie on a path to the destination, and therefore should expect to receive RREPs), and, learning-wise, would not add much to the experience you should have gained from Assignment 2.
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