diff options
Diffstat (limited to 'Documentation/networking')
| -rw-r--r-- | Documentation/networking/00-INDEX | 2 | ||||
| -rw-r--r-- | Documentation/networking/ieee802154.txt | 27 | ||||
| -rw-r--r-- | Documentation/networking/ifenslave.c | 2 | ||||
| -rw-r--r-- | Documentation/networking/ip-sysctl.txt | 25 | ||||
| -rw-r--r-- | Documentation/networking/openvswitch.txt | 195 | ||||
| -rw-r--r-- | Documentation/networking/team.txt | 2 |
6 files changed, 247 insertions, 6 deletions
diff --git a/Documentation/networking/00-INDEX b/Documentation/networking/00-INDEX index bbce1215434..9ad9ddeb384 100644 --- a/Documentation/networking/00-INDEX +++ b/Documentation/networking/00-INDEX @@ -144,6 +144,8 @@ nfc.txt - The Linux Near Field Communication (NFS) subsystem. olympic.txt - IBM PCI Pit/Pit-Phy/Olympic Token Ring driver info. +openvswitch.txt + - Open vSwitch developer documentation. operstates.txt - Overview of network interface operational states. packet_mmap.txt diff --git a/Documentation/networking/ieee802154.txt b/Documentation/networking/ieee802154.txt index f41ea240522..1dc1c24a754 100644 --- a/Documentation/networking/ieee802154.txt +++ b/Documentation/networking/ieee802154.txt @@ -78,3 +78,30 @@ in software. This is currently WIP. See header include/net/mac802154.h and several drivers in drivers/ieee802154/. +6LoWPAN Linux implementation +============================ + +The IEEE 802.15.4 standard specifies an MTU of 128 bytes, yielding about 80 +octets of actual MAC payload once security is turned on, on a wireless link +with a link throughput of 250 kbps or less. The 6LoWPAN adaptation format +[RFC4944] was specified to carry IPv6 datagrams over such constrained links, +taking into account limited bandwidth, memory, or energy resources that are +expected in applications such as wireless Sensor Networks. [RFC4944] defines +a Mesh Addressing header to support sub-IP forwarding, a Fragmentation header +to support the IPv6 minimum MTU requirement [RFC2460], and stateless header +compression for IPv6 datagrams (LOWPAN_HC1 and LOWPAN_HC2) to reduce the +relatively large IPv6 and UDP headers down to (in the best case) several bytes. + +In Semptember 2011 the standard update was published - [RFC6282]. +It deprecates HC1 and HC2 compression and defines IPHC encoding format which is +used in this Linux implementation. + +All the code related to 6lowpan you may find in files: net/ieee802154/6lowpan.* + +To setup 6lowpan interface you need (busybox release > 1.17.0): +1. Add IEEE802.15.4 interface and initialize PANid; +2. Add 6lowpan interface by command like: + # ip link add link wpan0 name lowpan0 type lowpan +3. Set MAC (if needs): + # ip link set lowpan0 address de:ad:be:ef:ca:fe:ba:be +4. Bring up 'lowpan0' interface diff --git a/Documentation/networking/ifenslave.c b/Documentation/networking/ifenslave.c index 65968fbf1e4..ac5debb2f16 100644 --- a/Documentation/networking/ifenslave.c +++ b/Documentation/networking/ifenslave.c @@ -539,12 +539,14 @@ static int if_getconfig(char *ifname) metric = 0; } else metric = ifr.ifr_metric; + printf("The result of SIOCGIFMETRIC is %d\n", metric); strcpy(ifr.ifr_name, ifname); if (ioctl(skfd, SIOCGIFMTU, &ifr) < 0) mtu = 0; else mtu = ifr.ifr_mtu; + printf("The result of SIOCGIFMTU is %d\n", mtu); strcpy(ifr.ifr_name, ifname); if (ioctl(skfd, SIOCGIFDSTADDR, &ifr) < 0) { diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index cb7f3148035..ad3e80e17b4 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -20,7 +20,7 @@ ip_no_pmtu_disc - BOOLEAN default FALSE min_pmtu - INTEGER - default 562 - minimum discovered Path MTU + default 552 - minimum discovered Path MTU route/max_size - INTEGER Maximum number of routes allowed in the kernel. Increase @@ -31,6 +31,16 @@ neigh/default/gc_thresh3 - INTEGER when using large numbers of interfaces and when communicating with large numbers of directly-connected peers. +neigh/default/unres_qlen_bytes - INTEGER + The maximum number of bytes which may be used by packets + queued for each unresolved address by other network layers. + (added in linux 3.3) + +neigh/default/unres_qlen - INTEGER + The maximum number of packets which may be queued for each + unresolved address by other network layers. + (deprecated in linux 3.3) : use unres_qlen_bytes instead. + mtu_expires - INTEGER Time, in seconds, that cached PMTU information is kept. @@ -165,6 +175,9 @@ tcp_congestion_control - STRING connections. The algorithm "reno" is always available, but additional choices may be available based on kernel configuration. Default is set as part of kernel configuration. + For passive connections, the listener congestion control choice + is inherited. + [see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ] tcp_cookie_size - INTEGER Default size of TCP Cookie Transactions (TCPCT) option, that may be @@ -282,11 +295,11 @@ tcp_max_ssthresh - INTEGER Default: 0 (off) tcp_max_syn_backlog - INTEGER - Maximal number of remembered connection requests, which are - still did not receive an acknowledgment from connecting client. - Default value is 1024 for systems with more than 128Mb of memory, - and 128 for low memory machines. If server suffers of overload, - try to increase this number. + Maximal number of remembered connection requests, which have not + received an acknowledgment from connecting client. + The minimal value is 128 for low memory machines, and it will + increase in proportion to the memory of machine. + If server suffers from overload, try increasing this number. tcp_max_tw_buckets - INTEGER Maximal number of timewait sockets held by system simultaneously. diff --git a/Documentation/networking/openvswitch.txt b/Documentation/networking/openvswitch.txt new file mode 100644 index 00000000000..b8a048b8df3 --- /dev/null +++ b/Documentation/networking/openvswitch.txt @@ -0,0 +1,195 @@ +Open vSwitch datapath developer documentation +============================================= + +The Open vSwitch kernel module allows flexible userspace control over +flow-level packet processing on selected network devices. It can be +used to implement a plain Ethernet switch, network device bonding, +VLAN processing, network access control, flow-based network control, +and so on. + +The kernel module implements multiple "datapaths" (analogous to +bridges), each of which can have multiple "vports" (analogous to ports +within a bridge). Each datapath also has associated with it a "flow +table" that userspace populates with "flows" that map from keys based +on packet headers and metadata to sets of actions. The most common +action forwards the packet to another vport; other actions are also +implemented. + +When a packet arrives on a vport, the kernel module processes it by +extracting its flow key and looking it up in the flow table. If there +is a matching flow, it executes the associated actions. If there is +no match, it queues the packet to userspace for processing (as part of +its processing, userspace will likely set up a flow to handle further +packets of the same type entirely in-kernel). + + +Flow key compatibility +---------------------- + +Network protocols evolve over time. New protocols become important +and existing protocols lose their prominence. For the Open vSwitch +kernel module to remain relevant, it must be possible for newer +versions to parse additional protocols as part of the flow key. It +might even be desirable, someday, to drop support for parsing +protocols that have become obsolete. Therefore, the Netlink interface +to Open vSwitch is designed to allow carefully written userspace +applications to work with any version of the flow key, past or future. + +To support this forward and backward compatibility, whenever the +kernel module passes a packet to userspace, it also passes along the +flow key that it parsed from the packet. Userspace then extracts its +own notion of a flow key from the packet and compares it against the +kernel-provided version: + + - If userspace's notion of the flow key for the packet matches the + kernel's, then nothing special is necessary. + + - If the kernel's flow key includes more fields than the userspace + version of the flow key, for example if the kernel decoded IPv6 + headers but userspace stopped at the Ethernet type (because it + does not understand IPv6), then again nothing special is + necessary. Userspace can still set up a flow in the usual way, + as long as it uses the kernel-provided flow key to do it. + + - If the userspace flow key includes more fields than the + kernel's, for example if userspace decoded an IPv6 header but + the kernel stopped at the Ethernet type, then userspace can + forward the packet manually, without setting up a flow in the + kernel. This case is bad for performance because every packet + that the kernel considers part of the flow must go to userspace, + but the forwarding behavior is correct. (If userspace can + determine that the values of the extra fields would not affect + forwarding behavior, then it could set up a flow anyway.) + +How flow keys evolve over time is important to making this work, so +the following sections go into detail. + + +Flow key format +--------------- + +A flow key is passed over a Netlink socket as a sequence of Netlink +attributes. Some attributes represent packet metadata, defined as any +information about a packet that cannot be extracted from the packet +itself, e.g. the vport on which the packet was received. Most +attributes, however, are extracted from headers within the packet, +e.g. source and destination addresses from Ethernet, IP, or TCP +headers. + +The <linux/openvswitch.h> header file defines the exact format of the +flow key attributes. For informal explanatory purposes here, we write +them as comma-separated strings, with parentheses indicating arguments +and nesting. For example, the following could represent a flow key +corresponding to a TCP packet that arrived on vport 1: + + in_port(1), eth(src=e0:91:f5:21:d0:b2, dst=00:02:e3:0f:80:a4), + eth_type(0x0800), ipv4(src=172.16.0.20, dst=172.18.0.52, proto=17, tos=0, + frag=no), tcp(src=49163, dst=80) + +Often we ellipsize arguments not important to the discussion, e.g.: + + in_port(1), eth(...), eth_type(0x0800), ipv4(...), tcp(...) + + +Basic rule for evolving flow keys +--------------------------------- + +Some care is needed to really maintain forward and backward +compatibility for applications that follow the rules listed under +"Flow key compatibility" above. + +The basic rule is obvious: + + ------------------------------------------------------------------ + New network protocol support must only supplement existing flow + key attributes. It must not change the meaning of already defined + flow key attributes. + ------------------------------------------------------------------ + +This rule does have less-obvious consequences so it is worth working +through a few examples. Suppose, for example, that the kernel module +did not already implement VLAN parsing. Instead, it just interpreted +the 802.1Q TPID (0x8100) as the Ethertype then stopped parsing the +packet. The flow key for any packet with an 802.1Q header would look +essentially like this, ignoring metadata: + + eth(...), eth_type(0x8100) + +Naively, to add VLAN support, it makes sense to add a new "vlan" flow +key attribute to contain the VLAN tag, then continue to decode the +encapsulated headers beyond the VLAN tag using the existing field +definitions. With this change, an TCP packet in VLAN 10 would have a +flow key much like this: + + eth(...), vlan(vid=10, pcp=0), eth_type(0x0800), ip(proto=6, ...), tcp(...) + +But this change would negatively affect a userspace application that +has not been updated to understand the new "vlan" flow key attribute. +The application could, following the flow compatibility rules above, +ignore the "vlan" attribute that it does not understand and therefore +assume that the flow contained IP packets. This is a bad assumption +(the flow only contains IP packets if one parses and skips over the +802.1Q header) and it could cause the application's behavior to change +across kernel versions even though it follows the compatibility rules. + +The solution is to use a set of nested attributes. This is, for +example, why 802.1Q support uses nested attributes. A TCP packet in +VLAN 10 is actually expressed as: + + eth(...), eth_type(0x8100), vlan(vid=10, pcp=0), encap(eth_type(0x0800), + ip(proto=6, ...), tcp(...))) + +Notice how the "eth_type", "ip", and "tcp" flow key attributes are +nested inside the "encap" attribute. Thus, an application that does +not understand the "vlan" key will not see either of those attributes +and therefore will not misinterpret them. (Also, the outer eth_type +is still 0x8100, not changed to 0x0800.) + +Handling malformed packets +-------------------------- + +Don't drop packets in the kernel for malformed protocol headers, bad +checksums, etc. This would prevent userspace from implementing a +simple Ethernet switch that forwards every packet. + +Instead, in such a case, include an attribute with "empty" content. +It doesn't matter if the empty content could be valid protocol values, +as long as those values are rarely seen in practice, because userspace +can always forward all packets with those values to userspace and +handle them individually. + +For example, consider a packet that contains an IP header that +indicates protocol 6 for TCP, but which is truncated just after the IP +header, so that the TCP header is missing. The flow key for this +packet would include a tcp attribute with all-zero src and dst, like +this: + + eth(...), eth_type(0x0800), ip(proto=6, ...), tcp(src=0, dst=0) + +As another example, consider a packet with an Ethernet type of 0x8100, +indicating that a VLAN TCI should follow, but which is truncated just +after the Ethernet type. The flow key for this packet would include +an all-zero-bits vlan and an empty encap attribute, like this: + + eth(...), eth_type(0x8100), vlan(0), encap() + +Unlike a TCP packet with source and destination ports 0, an +all-zero-bits VLAN TCI is not that rare, so the CFI bit (aka +VLAN_TAG_PRESENT inside the kernel) is ordinarily set in a vlan +attribute expressly to allow this situation to be distinguished. +Thus, the flow key in this second example unambiguously indicates a +missing or malformed VLAN TCI. + +Other rules +----------- + +The other rules for flow keys are much less subtle: + + - Duplicate attributes are not allowed at a given nesting level. + + - Ordering of attributes is not significant. + + - When the kernel sends a given flow key to userspace, it always + composes it the same way. This allows userspace to hash and + compare entire flow keys that it may not be able to fully + interpret. diff --git a/Documentation/networking/team.txt b/Documentation/networking/team.txt new file mode 100644 index 00000000000..5a013686b9e --- /dev/null +++ b/Documentation/networking/team.txt @@ -0,0 +1,2 @@ +Team devices are driven from userspace via libteam library which is here: + https://github.com/jpirko/libteam |