- TCP/IP Illustrated, Volume 2
- Addison-Wesley Professional Computing Series
- Preface
- Acknowledgments
- Structure Definitions
- Function and Macro Definitions
- 1. Introduction
- 1.1. Introduction
- 1.1. Introduction
- 1.2. Source Code Presentation
- 1.3. History
- 1.4. Application Programming Interfaces
- 1.5. Example Program
- 1.6. System Calls and Library Functions
- 1.7. Network Implementation Overview
- 1.8. Descriptors
- 1.9. Mbufs (Memory Buffers) and Output Processing
- 1.10. Input Processing
- 1.11. Network Implementation Overview Revisited
- 1.12. Interrupt Levels and Concurrency
- 1.13. Source Code Organization
- 1.14. Test Network
- 1.15. Summary
- 1.1. Introduction
- 2. Mbufs: Memory Buffers
- 2.1. Introduction
- 2.1. Introduction
- 2.2. Code Introduction
- 2.3. Mbuf Definitions
- 2.4. mbuf Structure
- 2.5. Simple Mbuf Macros and Functions
- 2.6. m_devget and m_pullup Functions
- 2.7. Summary of Mbuf Macros and Functions
- 2.8. Summary of Net/3 Networking Data Structures
- 2.9. m_copy and Cluster Reference Counts
- 2.10. Alternatives
- 2.11. Summary
- 2.1. Introduction
- 3. Interface Layer
- 3.1. Introduction
- 3.1. Introduction
- 3.2. Code Introduction
- 3.3. ifnet Structure
- 3.4. ifaddr Structure
- 3.5. sockaddr Structure
- 3.6. ifnet and ifaddr Specialization
- 3.7. Network Initialization Overview
- 3.8. Ethernet Initialization
- 3.9. SLIP Initialization
- 3.10. Loopback Initialization
- 3.11. if_attach Function
- 3.12. ifinit Function
- 3.13. Summary
- 3.1. Introduction
- 4. Interfaces: Ethernet
- 4.1. Introduction
- 4.1. Introduction
- 4.2. Code Introduction
- 4.3. Ethernet Interface
- leintr Function
- leread Function
- ether_input Function
- Broadcast and multicast recognition
- Link-level demultiplexing
- Queue the packet
- ether_output Function
- Host route
- Gateway route
- Avoid ARP flooding
- IP output
- Explicit Ethernet output
- Unrecognized address families
- Ethernet header
- lestart Function
- Interface must be initialized
- Dequeue frame from output queue
- Transmit frame and pass to BPF
- Repeat if device is ready for more frames
- Mark device as busy
- 4.4. ioctl System Call
- 4.5. Summary
- 4.1. Introduction
- 5. Interfaces: SLIP and Loopback
- 6. IP Addressing
- 6.1. Introduction
- 6.1. Introduction
- 6.2. Code Introduction
- 6.3. Interface and Address Summary
- 6.4. sockaddr_in Structure
- 6.5. in_ifaddr Structure
- 6.6. Address Assignment
- ifioctl Function
- in_control Function
- Preconditions: SIOCSIFADDR, SIOCSIFNETMASK, and SIOCSIFDSTADDR
- Superuser only
- Allocate structure
- Initialize structure
- Address Assignment: SIOCSIFADDR
- in_ifinit Function
- Assign address and notify hardware
- Ethernet configuration
- Discard previous routes
- Construct network mask and default subnetmask
- Construct network and subnetwork numbers
- Establish route for host or network
- Join all-hosts group
- Network Mask Assignment: SIOCSIFNETMASK
- Destination Address Assignment: SIOCSIFDSTADDR
- Retrieving Interface Information
- Multiple IP Addresses per Interface
- Additional IP Addresses: SIOCAIFADDR
- Deleting IP Addresses: SIOCDIFADDR
- 6.7. Interface ioctl Processing
- 6.8. Internet Utility Functions
- 6.9. ifnet Utility Functions
- 6.10. Summary
- 6.1. Introduction
- 7. Domains and Protocols
- 8. IP: Internet Protocol
- 8.1. Introduction
- 8.10. Summary
- 9. IP Option Processing
- 10. IP Fragmentation and Reassembly
- 11. ICMP: Internet Control Message Protocol
- 11.1. Introduction
- 11.1. Introduction
- 11.2. Code Introduction
- 11.3. icmp Structure
- 11.4. ICMP protosw Structure
- 11.5. Input Processing: icmp_input Function
- 11.6. Error Processing
- 11.7. Request Processing
- Echo Query: ICMP_ECHO and ICMP_ECHOREPLY
- Timestamp Query: ICMP_TSTAMP and ICMP_TSTAMPREPLY
- Address Mask Query: ICMP_MASKREQ and ICMP_MASKREPLY
- Select subnet mask
- Convert to reply
- Select destination address
- Information Query: ICMP_IREQ and ICMP_IREQREPLY
- Router Discovery: icmp_routeradvert and icmp_routersolicit
- 11.8. Redirect Processing
- 11.9. Reply Processing
- 11.10. Output Processing
- 11.11. icmp_error Function
- 11.12. icmp_reflect Function
- 11.13. icmp_send Function
- 11.14. icmp_sysctl Function
- 11.15. Summary
- 11.1. Introduction
- 12. IP Multicasting
- 12.1. Introduction
- 12.1. Introduction
- 12.2. Code Introduction
- 12.3. Ethernet Multicast Addresses
- 12.4. ether_multi Structure
- 12.5. Ethernet Multicast Reception
- 12.6. in_multi Structure
- 12.7. ip_moptions Structure
- 12.8. Multicast Socket Options
- 12.9. Multicast TTL Values
- 12.10. ip_setmoptions Function
- Construct the defaults
- Process options
- Discard structure if defaults are OK
- Selecting an Explicit Multicast Interface: IP_MULTICAST_IF
- Validation
- Select the default interface
- Selecting an Explicit Multicast TTL: IP_MULTICAST_TTL
- Validate and select the default TTL
- Selecting Multicast Loopbacks: IP_MULTICAST_LOOP
- Validate and select the loopback policy
- 12.11. Joining an IP Multicast Group
- Validation
- Locate the interface
- Already a member?
- Join the group
- in_addmulti Function
- Already a member
- Update the in_multi list
- Update the interface and announce the change
- slioctl and loioctl Functions: SIOCADDMULTI and SIOCDELMULTI
- leioctl Function: SIOCADDMULTI and SIOCDELMULTI
- ether_addmulti Function
- Initialize address range
- Already receiving
- Update ether_multi list
- 12.12. Leaving an IP Multicast Group
- 12.13. ip_getmoptions Function
- 12.14. Multicast Input Processing: ipintr Function
- 12.15. Multicast Output Processing: ip_output Function
- 12.16. Performance Considerations
- 12.17. Summary
- 12.1. Introduction
- 13. IGMP: Internet Group Management Protocol
- 14. IP Multicast Routing
- 14.1. Introduction
- 14.1. Introduction
- 14.2. Code Introduction
- 14.3. Multicast Output Processing Revisited
- 14.4. mrouted Daemon
- 14.5. Virtual Interfaces
- 14.6. IGMP Revisited
- 14.7. Multicast Routing
- 14.8. Multicast Forwarding: ip_mforward Function
- Arrival on physical interface
- Arrival on a tunnel
- Delete tunnel options
- Expired TTL or local multicast
- No route available
- Arrived on unexpected interface
- phyint_send Function
- tunnel_send Function
- Will the tunnel options fit?
- Duplicate the datagram and allocate mbuf for new header and tunnel options
- Modify IP header
- Construct tunnel options
- Send the tunneled datagram
- 14.9. Cleanup: ip_mrouter_done Function
- 14.10. Summary
- 14.1. Introduction
- 15. Socket Layer
- 15.1. Introduction
- 15.1. Introduction
- 15.2. Code Introduction
- 15.3. socket Structure
- 15.4. System Calls
- 15.5. Processes, Descriptors, and Sockets
- 15.6. socket System Call
- 15.7. getsock and sockargs Functions
- 15.8. bind System Call
- 15.9. listen System Call
- 15.10. tsleep and wakeup Functions
- 15.11. accept System Call
- 15.12. sonewconn and soisconnected Functions
- 15.13. connect System call
- 15.14. shutdown System Call
- 15.15. close System Call
- 15.16. Summary
- 15.1. Introduction
- 16. Socket I/O
- 16.1. Introduction
- 16.1. Introduction
- 16.2. Code Introduction
- 16.3. Socket Buffers
- 16.4. write, writev, sendto, and sendmsg System Calls
- 16.5. sendmsg System Call
- 16.6. sendit Function
- 16.7. sosend Function
- Reliable Protocol Buffering
- Unreliable Protocol Buffering
- sosend Code
- Lock send buffer
- Check for space
- Use data from top
- Copy data from process
- Pass data to the protocol
- Cleanup
- Compute transfer size and semantics
- If requested, disable routing
- Compute available space
- Enforce message size limit
- Wait for more space?
- Wait for space
- Allocate packet header or standard mbuf
- If possible, use a cluster
- Prepare the mbuf
- Get data from the process
- Fill another buffer?
- sosend Summary
- Performance Considerations
- 16.8. read, readv, recvfrom, and recvmsg System Calls
- 16.9. recvmsg System Call
- 16.10. recvit Function
- 16.11. soreceive Function
- 16.12. soreceive Code
- If necessary, wait for data
- Process address and control information
- Setup data transfer
- Mbuf data transfer loop
- Cleanup
- Receive OOB data
- Connection confirmation
- Can the call be satisfied now?
- Wait for more data?
- Yes, wait for more data
- dontblock
- Return address information
- Return control information
- Prepare to transfer data
- Check for transition between OOB and regular data
- Update OOB mark
- Finished with mbuf?
- More data to process
- Update OOB mark
- End of logical record
- MSG_WAITALL
- Error or no more data will arrive
- Wait for data to arrive
- Synchronize m and nextrecord with receive buffer
- Process next mbuf
- Truncated message
- End of record processing
- Nothing transferred
- Analysis
- 16.13. select System Call
- Validation and setup
- Copy file descriptor sets from process
- Setup timeout value
- Scan file descriptors
- Error or some descriptors are ready
- Timeout expired?
- Status changed during selscan
- Wait for buffer changes
- Ready to return
- selscan Function
- Locate descriptors to be monitored
- Poll descriptor
- Descriptor is ready
- soo_select Function
- Is socket readable?
- Is socket writeable?
- Are there any exceptional conditions pending?
- selrecord Function
- Already selecting on this descriptor
- Select collision with another process?
- No collision
- selwakeup Function
- Wake all processes during a collision
- 16.14. Summary
- 16.1. Introduction
- 17. Socket Options
- 18. Radix Tree Routing Tables
- 18.1. Introduction
- 18.1. Introduction
- 18.2. Routing Table Structure
- 18.3. Routing Sockets
- 18.4. Code Introduction
- 18.5. Radix Node Data Structures
- 18.6. Routing Structures
- 18.7. Initialization: route_init and rtable_init Functions
- 18.8. Initialization: rn_init and rn_inithead Functions
- 18.9. Duplicate Keys and Mask Lists
- 18.10. rn_match Function
- 18.11. rn_search Function
- 18.12. Summary
- 18.1. Introduction
- 19. Routing Requests and Routing Messages
- 19.1. Introduction
- 19.1. Introduction
- 19.2. rtalloc and rtalloc1 Functions
- 19.3. RTFREE Macro and rtfree Function
- 19.4. rtrequest Function
- Delete from routing tree
- Remove reference to gateway routing table entry
- Call interface request function
- Return pointer or release reference
- Locate corresponding interface
- Allocate memory for routing table entry
- Allocate and copy gateway address
- Copy destination address
- Add entry to routing tree
- Store interface pointers
- Copy metrics for newly cloned route
- Call interface request function
- Return pointer and increment reference count
- Example: Cloned Routes with Network Masks
- 19.5. rt_setgate Function
- 19.6. rtinit Function
- 19.7. rtredirect Function
- 19.8. Routing Message Structures
- 19.9. rt_missmsg Function
- 19.10. rt_ifmsg Function
- 19.11. rt_newaddrmsg Function
- 19.12. rt_msg1 Function
- 19.13. rt_msg2 Function
- 19.14. sysctl_rtable Function
- 19.15. sysctl_dumpentry Function
- 19.16. sysctl_iflist Function
- 19.17. Summary
- 19.1. Introduction
- 20. Routing Sockets
- 20.1. Introduction
- 20.1. Introduction
- 20.2. routedomain and protosw Structures
- 20.3. Routing Control Blocks
- 20.4. raw_init Function
- 20.5. route_output Function
- Check mbuf for validity
- Allocate buffer
- Check version number
- Destination address required
- Handle optional genmask
- Locate existing entry
- Do not allow network match
- Use network mask to find correct entry
- Return destination, gateway, and masks
- Return interface information
- Construct reply
- Change gateway
- Locate new interface
- Check if interface changed
- Update metrics
- Call interface request function
- Store clone generation mask
- Update bitmask of locked metrics
- Return error or OK
- Release held route
- No process to receive message
- Other listeners but no loopback copy
- Convert buffer into mbuf chain
- Avoid loopback copy
- Set address family of routing message
- 20.6. rt_xaddrs Function
- 20.7. rt_setmetrics Function
- 20.8. raw_input Function
- 20.9. route_usrreq Function
- 20.10. raw_usrreq Function
- 20.11. raw_attach, raw_detach, and raw_disconnect Functions
- 20.12. Summary
- 20.1. Introduction
- 21. ARP: Address Resolution Protocol
- 21.1. Introduction
- 21.1. Introduction
- 21.2. ARP and the Routing Table
- 21.3. Code Introduction
- 21.4. ARP Structures
- 21.5. arpwhohas Function
- 21.6. arprequest Function
- 21.7. arpintr Function
- 21.8. in_arpinput Function
- Look for matching interface and IP address
- Validate sender’s hardware address
- Check sender’s IP address
- Search routing table for match with sender’s IP address
- Update existing entry or fill in new entry
- Check if sender’s hardware addresses changed
- Record sender’s hardware address
- Update newly resolved ARP entry
- Finished with ARP reply packets
- This host is the target
- Check if this host is a proxy server for target
- Form proxy reply
- Complete construction of ARP reply packet
- Fill in sockaddr with Ethernet header
- 21.9. ARP Timer Functions
- 21.10. arpresolve Function
- 21.11. arplookup Function
- 21.12. Proxy ARP
- 21.13. arp_rtrequest Function
- Initialize ARP timeout function
- Ignore indirect routes
- RTM_ADD command
- Backward compatibility
- Initialize entry for network route to interface
- Send gratuitous ARP request
- Verify sockaddr_dl Structure
- Handle route changes
- Initialize llinfo_arp structure
- Handle local host specially
- Make entry permanent and set Ethernet address
- Set interface pointer to loopback interface
- Verify la pointer
- Delete llinfo_arp structure
- 21.14. ARP and Multicasting
- 21.15. Summary
- 21.1. Introduction
- 22. Protocol Control Blocks
- 22.1. Introduction
- 22.1. Introduction
- 22.2. Code Introduction
- 22.3. inpcb Structure
- 22.4. in_pcballoc and in_pcbdetach Functions
- 22.5. Binding, Connecting, and Demultiplexing
- 22.6. in_pcblookup Function
- 22.7. in_pcbbind Function
- 22.8. in_pcbconnect Function
- Validate argument
- Handle connection to 0.0.0.0 and 255.255.255.255 specially
- Release route if no longer valid
- Acquire route
- Determine outgoing interface
- Verify that socket pair is unique
- Implicit bind and assignment of ephemeral port
- Store foreign address and foreign port in PCB
- IP Source Address Versus Outgoing Interface Address
- 22.9. in_pcbdisconnect Function
- 22.10. in_setsockaddr and in_setpeeraddr Functions
- 22.11. in_pcbnotify, in_rtchange, and in_losing Functions
- 22.12. Implementation Refinements
- 22.13. Summary
- 22.1. Introduction
- 23. UDP: User Datagram Protocol
- 23.1. Introduction
- 23.1. Introduction
- 23.2. Code Introduction
- 23.3. UDP protosw Structure
- 23.4. UDP Header
- 23.5. udp_init Function
- 23.6. udp_output Function
- Discard optional control information
- Temporarily connect an unconnected socket
- Prepend IP and UDP headers
- Prepending IP/UDP Headers and Mbuf Clusters
- UDP Checksum Calculation and Pseudo-Header
- Prepare pseudo-header for checksum computation
- Calculate checksum
- Fill in UDP length, TTL, and TOS
- Send datagram
- Disconnect temporarily connected socket
- 23.7. udp_input Function
- General Validation of Received UDP Datagram
- Discard IP options
- Verify UDP length
- Save copy of IP header and verify UDP checksum
- Demultiplexing Unicast Datagrams
- Check one-behind cache
- Search all UDP PCBs
- Generate ICMP port unreachable error
- Return source IP address and source port
- IP_RECVDSTADDR socket option
- Unimplemented socket options
- Append data to socket’s receive queue
- Error return
- Demultiplexing Multicast and Broadcast Datagrams
- Connected UDP Sockets and Multihomed Hosts
- 23.8. udp_saveopt Function
- 23.9. udp_ctlinput Function
- 23.10. udp_usrreq Function
- 23.11. udp_sysctl Function
- 23.12. Implementation Refinements
- 23.13. Summary
- 23.1. Introduction
- 24. TCP: Transmission Control Protocol
- 25. TCP Timers
- 25.1. Introduction
- 25.1. Introduction
- 25.2. Code Introduction
- 25.3. tcp_canceltimers Function
- 25.4. tcp_fasttimo Function
- 25.5. tcp_slowtimo Function
- 25.6. tcp_timers Function
- FIN_WAIT_2 and 2MSL Timers
- 2MSL timer
- FIN_WAIT_2 timer
- Persist Timer
- Force window probe segment
- Connection Establishment and Keepalive Timers
- Connection-establishment timer expires after 75 seconds
- Keepalive timer expires after 2 hours of idle time
- Drop connection when no response
- Send a keepalive probe
- Reset keepalive timer
- 25.7. Retransmission Timer Calculations
- 25.8. tcp_newtcpcb Function
- 25.9. tcp_setpersist Function
- 25.10. tcp_xmit_timer Function
- 25.11. Retransmission Timeout: tcp_timers Function
- 25.12. An RTT Example
- 25.13. Summary
- 25.1. Introduction
- 26. TCP Output
- 26.1. Introduction
- 26.1. Introduction
- 26.2. tcp_output Overview
- 26.3. Determine if a Segment Should be Sent
- 26.4. TCP Options
- 26.5. Window Scale Option
- 26.6. Timestamp Option
- 26.7. Send a Segment
- Build MSS option
- Should window scale option be sent?
- Build window scale option
- Should timestamp option be sent?
- Build timestamp option
- Check if options have overflowed segment
- Update statistics
- Allocate an mbuf for IP and TCP headers
- Copy data into mbuf
- Set PSH flag
- Update statistics
- Get mbuf for IP and TCP headers
- Copy IP and TCP header templates into mbuf
- Decrement snd_nxt if FIN is being retransmitted
- Set sequence number field of segment
- Set acknowledgment field of segment
- Set header length if options present
- Don’t advertise less than one full-sized segment
- Observe upper limit for advertised window on this connection
- Do not shrink window
- Set urgent offset
- Remember starting sequence number
- Increment snd_nxt
- Update snd_max
- Set retransmission timer
- Persist state
- Add trace record for socket debugging
- Set IP length, TTL, and TOS
- Pass datagram to IP
- Update rcv_adv and last_ack_sent
- More data to send?
- 26.8. tcp_template Function
- 26.9. tcp_respond Function
- 26.10. Summary
- 26.1. Introduction
- 27. TCP Functions
- 27.1. Introduction
- 27.1. Introduction
- 27.2. tcp_drain Function
- 27.3. tcp_drop Function
- 27.4. tcp_close Function
- 27.5. tcp_mss Function
- Acquire a route if necessary
- Initialize smoothed RTT estimator
- Initialize smoothed mean deviation estimator
- Calculate initial RTO
- Use MSS from routing table MTU
- Round MSS down to multiple of MCLBYTES
- Check if destination local or nonlocal
- Other end’s MSS is upper bound
- Round buffer sizes to multiple of MSS
- Initialize congestion window and slow start threshold
- Example
- 27.6. tcp_ctlinput Function
- 27.7. tcp_notify Function
- 27.8. tcp_quench Function
- 27.9. TCP_REASS Macro and tcp_reass Function
- 27.10. tcp_trace Function
- 27.11. Summary
- 27.1. Introduction
- 28. TCP Input
- 28.1. Introduction
- 28.1. Introduction
- 28.2. Preliminary Processing
- Get IP and TCP headers in first mbuf
- Verify TCP checksum
- Verify TCP offset field
- Get headers plus option into first mbuf
- Process timestamp option quickly
- Save input flags and convert fields to host byte order
- Locate Internet PCB
- Drop segment and generate RST
- Silently drop segment
- Unscale advertised window
- Save connection state and IP/TCP headers if socket debug option enabled
- Create new socket if segment arrives for listening socket
- Compute window scale factor
- Reset idle time and keepalive timer
- Process TCP options if not in LISTEN state
- 28.3. tcp_dooptions Function
- 28.4. Header Prediction
- Check if segment is the next expected
- Update ts_recent from received timestamp
- Test for pure ACK
- Update RTT estimators
- Delete acknowledged bytes from send buffer
- Stop retransmit timer
- Awaken waiting processes
- Generate more output
- Test for next in-sequence data segment
- Complete processing of received data
- Statistics
- 28.5. TCP Input: Slow Path Processing
- 28.6. Initiation of Passive Open, Completion of Active Open
- Initiation of Passive Open
- Drop if RST, ACK, or no SYN
- Drop if broadcast or multicast
- Get mbuf for client’s IP address and port
- Set local address in PCB
- Connect PCB to peer
- Allocate and initialize IP and TCP header template
- Process any TCP options
- Initialize ISS
- Initialize sequence number variables in control block
- ACK the SYN and change state
- Completion of Active Open
- Verify received ACK
- Process and drop RST segment
- Verify SYN flag set
- Process ACK
- Turn off retransmission timer
- Initialize receive sequence numbers
- Connection is established
- Check for window scale option
- Pass any queued data to process
- Update RTT estimators
- Simultaneous open
- Drop any received data that follows receive window
- Force update of window variables
- 28.7. PAWS: Protection Against Wrapped Sequence Numbers
- 28.8. Trim Segment so Data is Within Window
- Check if any duplicate data at front of segment
- Remove duplicate SYN
- Check for entire duplicate packet
- Check for duplicate FIN
- Generate duplicate ACK
- Handle simultaneous open or self-connect
- Update statistics for partial duplicate segments
- Remove duplicate data and update urgent offset
- Calculate number of bytes beyond right edge of window
- Check for new incarnation of a connection in the TIME_WAIT state
- Check for probe of closed window
- Drop other segments that are completely outside window
- Handle segments that contain some valid data
- When to Drop an ACK
- 28.9. Self-Connects and Simultaneous Opens
- 28.10. Record Timestamp
- 28.11. RST Processing
- 28.12. Summary
- 28.1. Introduction
- 29. TCP Input
- 29.1. Introduction
- 29.1. Introduction
- 29.2. ACK Processing Overview
- 29.3. Completion of Passive Opens and Simultaneous Opens
- 29.4. Fast Retransmit and Fast Recovery Algorithms
- 29.5. ACK Processing
- Adjust congestion window
- Check for out-of-range ACK
- Calculate number of bytes acknowledged
- Update RTT estimators
- Check if all outstanding data has been acknowledged
- Unacknowledged data outstanding
- Karn’s Algorithm and Timestamps
- Update congestion window
- Remove acknowledged bytes from the send buffer
- Wakeup processes waiting on send buffer
- Receipt of ACK in FIN_WAIT_1 state
- Set FIN_WAIT_2 timer
- Receipt of ACK in CLOSING state
- Receipt of ACK in LAST_ACK state
- Receipt of ACK in TIME WAIT state
- 29.6. Update Window Information
- 29.7. Urgent Mode Processing
- 29.8. tcp_pulloutofband Function
- 29.9. Processing of Received Data
- 29.10. FIN Processing
- 29.11. Final Processing
- 29.12. Implementation Refinements
- 29.13. Header Compression
- 29.14. Summary
- 29.1. Introduction
- 30. TCP User Requests
- 30.1. Introduction
- 30.1. Introduction
- 30.2. tcp_usrreq Function
- in_control processes ioctl requests
- Control information is invalid
- PRU_ATTACH request
- PRU_DETACH request
- Assign ephemeral port
- Connect PCB
- Initialize IP and TCP headers
- Calculate window scale factor
- Set socket and connection state
- Initialize sequence numbers
- Send initial SYN
- PRU_SHUTDOWN request
- PRU_RCVD request
- PRU_SEND request
- PRU_ABORT request
- PRU_SENSE request
- Verify that reading out-of-band data is appropriate
- Check that out-of-band byte has arrived
- Return out-of-band byte
- Flip flags
- Check for room and append to send buffer
- Calculate urgent pointer
- Force TCP output
- 30.3. tcp_attach Function
- 30.4. tcp_disconnect Function
- 30.5. tcp_usrclosed Function
- 30.6. tcp_ctloutput Function
- 30.7. Summary
- 30.1. Introduction
- 31. BPF: BSD Packet Filter
- 32. Raw IP
- Epilogue
- A. Solutions to Selected Exercises
- Chapter 1
- Chapter 1
- Chapter 2
- Chapter 3
- Chapter 4
- Chapter 5
- Chapter 6
- Chapter 7
- Chapter 8
- Chapter 9
- Chapter 10
- Chapter 11
- Chapter 12
- Chapter 13
- Chapter 14
- Chapter 15
- Chapter 16
- Chapter 17
- Chapter 18
- Chapter 19
- Chapter 20
- Chapter 21
- Chapter 22
- Chapter 23
- Chapter 24
- Chapter 25
- Chapter 26
- Chapter 27
- Chapter 28
- Chapter 29
- Chapter 30
- Chapter 31
- Chapter 32
- Chapter 1
- B. Source Code Availability
- C. RFC 1122 Compliance
- C.1. Link-Layer Requirements
- Bibliography
This text uses URLs to specify the location and method of access of resources on the Internet. For example, the common “anonymous FTP” technique is designated as
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There are numerous ways to obtain the 4.4BSD-Lite release. The entire 4.4BSD-Lite release is available from Walnut Creek CD-ROM as
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O’Reilly & Associates publishes the entire set of 4.4BSD manuals along with the 4.4BSD-Lite release on CD-ROM. Contact 1 800 889 8969 or +1 707 829 0515.
The 4.4BSD-Lite release is not a complete operating system. To experiment with the networking software described in this text you need an operating system that is built from the 4.4BSD-Lite release or an environment that supports the 4.4BSD-Lite networking code.
The operating system used by the authors is commercially available from Berkeley Software Design, Inc. Contact 1 800 ITS BSD8, +1 719 260 8114, or [email protected] for additional information.
There are also freely available operating systems built on 4.4BSD-Lite. These are known by the names NetBSD, 386BSD, and FreeBSD. Additional information is available from Walnut Creek CD-ROM (ftp.cdrom.com) or on the various comp.os.386bsd Usenet newsgroups.
All RFCs are available at no charge through electronic mail or by using anonymous FTP across the Internet. Sending electronic mail as shown here:
To: [email protected] Subject: getting rfcs help: ways_to_get_rfcs
returns a detailed listing of various ways to obtain the RFCs using either email or anonymous FTP.
Remember that the starting place is to obtain the current index and look up the RFC that you want in the index. This entry tells you if that RFC has been made obsolete or updated by a newer RFC.
The GNU Indent program was used to format all the source code presented in the text, and the GNU Gzip program is often used on the Internet to compress files. These programs are available as
ftp://prep.ai.mit.edu/pub/gnu/indent-1.9.1.tar.gz ftp://prep.ai.mit.edu/pub/gnu/gzip-1.2.2.tar
The numbers in the filenames will change as newer versions are released. There are also versions of the Gzip program for other operating systems, such as MS-DOS.
There are many sites around the world that also provide the GNU archives, and the FTP greeting on prep.ai.mit.edu displays their names.
There are several freely available implementations of PPP. Part 5 of the comp.protocols.ppp FAQ is a good place to start:
Current releases of the mrouted software as well as other multicast applications can be found at the Xerox Palo Alto Research Center:
An SNMP agent implementation compatible with Net/3 is part of the ISODE software package. For more information, start with the ISODE Consortium’s World Wide Web page at
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