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Diffstat (limited to 'doc/bird.sgml')
| -rw-r--r-- | doc/bird.sgml | 262 |
1 files changed, 195 insertions, 67 deletions
diff --git a/doc/bird.sgml b/doc/bird.sgml index d1a3b70f..a4d7cb0c 100644 --- a/doc/bird.sgml +++ b/doc/bird.sgml @@ -14,7 +14,7 @@ configuration - something in config which is not keyword. (set-fill-column 80) - Copyright 1999,2000 Pavel Machek <pavel@ucw.cz>, distribute under GPL version 2 or later. + Copyright 1999 - 2022 CZ.NIC, z.s.p.o , distribute under GPL version 2 or later. --> @@ -23,7 +23,6 @@ configuration - something in config which is not keyword. <title>BIRD 2.0 User's Guide <author> Ondrej Filip <it/<feela@network.cz>/, -Pavel Machek <it/<pavel@ucw.cz>/, Martin Mares <it/<mj@ucw.cz>/, Maria Matejka <it/<mq@jmq.cz>/, Ondrej Zajicek <it/<santiago@crfreenet.org>/ @@ -145,13 +144,6 @@ BIRD executable by configuring out routing protocols you don't use, and <p>You can pass several command-line options to bird: <descrip> - <tag><label id="argv-block">-B <m/exp/</tag> - allocate memory using 2^<cf/exp/ byte sized blocks; - if you're expecting high memory load, raise this to - reduce number of allocated memory pages. For a million routes - in one table, the recommended setting is 18. - Default is your system page size, typically 12 for 4096 bytes. - <tag><label id="argv-config">-c <m/config name/</tag> use given configuration file instead of <it/prefix/<file>/etc/bird.conf</file>. @@ -259,16 +251,9 @@ The global best route selection algorithm is (roughly) as follows: </itemize> <p><label id="dsc-table-sorted">Usually, a routing table just chooses a selected -route from a list of entries for one network. But if the <cf/sorted/ option is -activated, these lists of entries are kept completely sorted (according to -preference or some protocol-dependent metric). This is needed for some features -of some protocols (e.g. <cf/secondary/ option of BGP protocol, which allows to -accept not just a selected route, but the first route (in the sorted list) that -is accepted by filters), but it is incompatible with some other features (e.g. -<cf/deterministic med/ option of BGP protocol, which activates a way of choosing -selected route that cannot be described using comparison and ordering). Minor -advantage is that routes are shown sorted in <cf/show route/, minor disadvantage -is that it is slightly more computationally expensive. +route from a list of entries for one network. Optionally, these lists of entries +are kept completely sorted (according to preference or some protocol-dependent +metric). See <ref id="rtable-sorted" name="sorted"> table option for details. <sect>Routes and network types <label id="routes"> @@ -635,18 +620,97 @@ include "tablename.conf";; <cf/protocol/ times, and the <cf/iso long ms/ format for <cf/base/ and <cf/log/ times. - <tag><label id="opt-table"><m/nettype/ table <m/name/ [sorted]</tag> - Create a new routing table. The default routing tables <cf/master4/ and - <cf/master6/ are created implicitly, other routing tables have to be - added by this command. Option <cf/sorted/ can be used to enable sorting - of routes, see <ref id="dsc-table-sorted" name="sorted table"> - description for details. + <tag><label id="opt-table"><m/nettype/ table <m/name/ [ { <m/option/; [<m/.../] } ]</tag> + Define a new routing table. The default routing tables <cf/master4/ and + <cf/master6/ are defined implicitly, other routing tables have to be + defined by this option. See the <ref id="rtable-opts" + name="routing table configuration section"> for routing table options. <tag><label id="opt-eval">eval <m/expr/</tag> Evaluates given filter expression. It is used by the developers for testing of filters. </descrip> +<sect>Routing table options +<label id="rtable-opts"> + +<p>Most routing tables do not need any options and are defined without an option +block, but there are still some options to tweak routing table behavior. Note +that implicit tables (<cf/master4/ and <cf/master6/) can be redefined in order +to set options. + +<descrip> + <tag><label id="rtable-sorted">sorted <m/switch/</tag> + Usually, a routing table just chooses the selected (best) route from a + list of routes for each network, while keeping remaining routes unsorted. + If enabled, these lists of routes are kept completely sorted (according + to preference or some protocol-dependent metric). + + This is needed for some protocol features (e.g. <cf/secondary/ option of + BGP protocol, which allows to accept not just a selected route, but the + first route (in the sorted list) that is accepted by filters), but it is + incompatible with some other features (e.g. <cf/deterministic med/ + option of BGP protocol, which activates a way of choosing selected route + that cannot be described using comparison and ordering). Minor advantage + is that routes are shown sorted in <cf/show route/, minor disadvantage + is that it is slightly more computationally expensive. Default: off. + + <tag><label id="rtable-trie">trie <m/switch/</tag> + BIRD routing tables are implemented with hash tables, which is efficient + for exact-match lookups, but inconvenient for longest-match lookups or + interval lookups (finding superprefix or subprefixes). This option + activates additional trie structure that is used to accelerate these + lookups, while using the hash table for exact-match lookups. + + This has advantage for <ref id="rpki" name="RPKI"> (on ROA tables), + for <ref id="bgp-gateway" name="recursive next-hops"> (on IGP tables), + and is required for <ref id="bgp-validate" name="flowspec validation"> + (on base IP tables). Another advantage is that interval results (like + from <cf/show route in .../ command) are lexicographically sorted. The + disadvantage is that trie-enabled routing tables require more memory, + which may be an issue especially in multi-table setups. Default: off. + + <tag><label id="rtable-min-settle-time">min settle time <m/time/</tag> + Specify a minimum value of the settle time. When a ROA table changes, + automatic <ref id="proto-rpki-reload" name="RPKI reload"> may be + triggered, after a short settle time. Minimum settle time is a delay + from the last ROA table change to wait for more updates. Default: 1 s. + + + <tag><label id="rtable-max-settle-time">max settle time <m/time/</tag> + Specify a maximum value of the settle time. When a ROA table changes, + automatic <ref id="proto-rpki-reload" name="RPKI reload"> may be + triggered, after a short settle time. Maximum settle time is an upper + limit to the settle time from the initial ROA table change even if + there are consecutive updates gradually renewing the settle time. + Default: 20 s. + + <tag><label id="rtable-gc-threshold">gc threshold <m/number/</tag> + Specify a minimum amount of removed networks that triggers a garbage + collection (GC) cycle. Default: 1000. + + <tag><label id="rtable-gc-period">gc period <m/time/</tag> + Specify a period of time between consecutive GC cycles. When there is a + significant amount of route withdraws, GC cycles are executed repeatedly + with given period time (with some random factor). When there is just + small amount of changes, GC cycles are not executed. In extensive route + server setups, running GC on hundreds of full BGP routing tables can + take significant amount of time, therefore they should use higher GC + periods. Default: adaptive, based on number of routing tables in the + configuration. From 10 s (with <= 25 routing tables) up to 600 s (with + >= 1500 routing tables). + + <tag><label id="rtable-cork-threshold">cork threshold <m/number/ <m/number/</tag> + Too many pending exports may lead to memory bloating. In such cases, + BIRD tries to relieve the memory pressure by pausing some routines until + the queue sizes get low enough. This option allows the user to set the + thresholds; first value is the low threshold (when to resume), the + second one is the high threshold (when to pause). The higher is the + threshold, the more memory can get used. In most cases, the defaults + should work for you. Default: 128, 512. +</descrip> + + <sect>Protocol options <label id="protocol-opts"> @@ -874,10 +938,12 @@ inherited from templates can be updated by new definitions. <cf/none/ is for dropping all routes. Default: <cf/all/ (except for EBGP). - <tag><label id="proto-export">export <m/filter/</tag> + <tag><label id="proto-export">export [ in <m/prefix/ ] <m/filter/</tag> This is similar to the <cf>import</cf> keyword, except that it works in - the direction from the routing table to the protocol. Default: <cf/none/ - (except for EBGP). + the direction from the routing table to the protocol. If <cf/in/ keyword is used, + only routes inside the given prefix are exported. Other routes are completely + ignored (e.g. no logging and no statistics). + Default: <cf/none/ (except for EBGP). <tag><label id="proto-import-keep-filtered">import keep filtered <m/switch/</tag> Usually, if an import filter rejects a route, the route is forgotten. @@ -1205,8 +1271,8 @@ this: <code> filter not_too_far -int var; { + int var; if defined( rip_metric ) then var = rip_metric; else { @@ -1235,9 +1301,9 @@ local variables. Recursion is not allowed. Function definitions look like this: <code> function name () -int local_variable; { - local_variable = 5; + int local_variable; + int another_variable = 5; } function with_parameters (int parameter) @@ -1246,16 +1312,19 @@ function with_parameters (int parameter) } </code> -<p>Unlike in C, variables are declared after the <cf/function/ line, but before -the first <cf/{/. You can't declare variables in nested blocks. Functions are -called like in C: <cf>name(); with_parameters(5);</cf>. Function may return -values using the <cf>return <m/[expr]/</cf> command. Returning a value exits -from current function (this is similar to C). +<p>Like in C programming language, variables are declared inside function body, +either at the beginning, or mixed with other statements. Declarations may +contain initialization. You can also declare variables in nested blocks, such +variables have scope restricted to such block. There is a deprecated syntax to +declare variables after the <cf/function/ line, but before the first <cf/{/. +Functions are called like in C: <cf>name(); with_parameters(5);</cf>. Function +may return values using the <cf>return <m/[expr]/</cf> command. Returning a +value exits from current function (this is similar to C). -<p>Filters are defined in a way similar to functions except they can't have +<p>Filters are defined in a way similar to functions except they cannot have explicit parameters. They get a route table entry as an implicit parameter, it is also passed automatically to any functions called. The filter must terminate -with either <cf/accept/ or <cf/reject/ statement. If there's a runtime error in +with either <cf/accept/ or <cf/reject/ statement. If there is a runtime error in filter, the route is rejected. <p>A nice trick to debug filters is to use <cf>show route filter <m/name/</cf> @@ -1299,6 +1368,9 @@ in the foot). The same syntax can also be used to construct a pair from two arbitrary integer expressions (for example <cf/(1+2,a)/). + Operators <cf/.asn/ and <cf/.data/ can be used to extract corresponding + components of a pair: <cf>(<m/asn/, <m/data/)</cf>. + <tag><label id="type-quad">quad</tag> This is a dotted quad of numbers used to represent router IDs (and others). Each component can have a value from 0 to 255. Literals of @@ -1389,6 +1461,10 @@ in the foot). pairs, LCs can be constructed using expressions for its parts, (e.g. <cf/(myas, 10+20, 3*10)/, where <cf/myas/ is an integer variable). + Operators <cf/.asn/, <cf/.data1/, and <cf/.data2/ can be used + to extract corresponding components of LCs: + <cf>(<m/asn/, <m/data1/, <m/data2/)</cf>. + <tag><label id="type-set">int|pair|quad|ip|prefix|ec|lc|enum set</tag> Filters recognize four types of sets. Sets are similar to strings: you can pass them around but you can't modify them. Literals of type <cf>int @@ -1532,7 +1608,7 @@ in the foot). Clist is similar to a set, except that unlike other sets, it can be modified. The type is used for community list (a set of pairs) and for cluster list (a set of quads). There exist no literals of this type. - There are three special operators on clists: + There are special operators on clists: <cf><m/C/.len</cf> returns the length of clist <m/C/. @@ -1559,6 +1635,15 @@ in the foot). <cf><m/C/.add(<m/P/);</cf> if <m/C/ is appropriate route attribute (for example <cf/bgp_community/). Similarly for <cf/delete/ and <cf/filter/. + <cf><m/C/.min</cf> returns the minimum element of clist <m/C/. + + <cf><m/C/.max</cf> returns the maximum element of clist <m/C/. + + Operators <cf/.min/, <cf/.max/ can be used together with <cf/filter/ + to extract the community from the specific subset of communities + (e.g. localpref or prepend) without the need to check every possible + value (e.g. <cf/filter(bgp_community, [(23456, 1000..1099)]).min/). + <tag><label id="type-eclist">eclist</tag> Eclist is a data type used for BGP extended community lists. Eclists are very similar to clists, but they are sets of ECs instead of pairs. @@ -1609,7 +1694,8 @@ prefix and an ASN as arguments. <sect>Control structures <label id="control-structures"> -<p>Filters support two control structures: conditions and case switches. +<p>Filters support several control structures: conditions, for loops and case +switches. <p>Syntax of a condition is: <cf>if <M>boolean expression</M> then <m/commandT/; else <m/commandF/;</cf> and you can use <cf>{ <m/command1/; <m/command2/; @@ -1617,6 +1703,14 @@ else <m/commandF/;</cf> and you can use <cf>{ <m/command1/; <m/command2/; omitted. If the <cf><m>boolean expression</m></cf> is true, <m/commandT/ is executed, otherwise <m/commandF/ is executed. +<p>For loops allow to iterate over elements in compound data like BGP paths or +community lists. The syntax is: <cf>for [ <m/type/ ] <m/variable/ in <m/expr/ +do <m/command/;</cf> and you can also use compound command like in conditions. +The expression is evaluated to a compound data, then for each element from such +data the command is executed with the item assigned to the variable. A variable +may be an existing one (when just name is used) or a locally defined (when type +and name is used). In both cases, it must have the same type as elements. + <p>The <cf>case</cf> is similar to case from Pascal. Syntax is <cf>case <m/expr/ { else: | <m/num_or_prefix [ .. num_or_prefix]/: <m/statement/ ; [ ... ] }</cf>. The expression after <cf>case</cf> can be of any type which can be @@ -1629,16 +1723,21 @@ neither of the <cf/:/ clauses, the statements after <cf/else:/ are executed. <p>Here is example that uses <cf/if/ and <cf/case/ structures: <code> +if 1234 = i then printn "."; else { + print "not 1234"; + print "You need {} around multiple commands"; +} + +for int asn in bgp_path do { + printn "ASN: ", asn; + if asn < 65536 then print " (2B)"; else print " (4B)"; +} + case arg1 { 2: print "two"; print "I can do more commands without {}"; 3 .. 5: print "three to five"; else: print "something else"; } - -if 1234 = i then printn "."; else { - print "not 1234"; - print "You need {} around multiple commands"; -} </code> @@ -1667,17 +1766,8 @@ Common route attributes are: primary key of the routing table. Read-only. (See the <ref id="routes" name="chapter about routes">.) - <tag><label id="rta-scope"><m/enum/ scope</tag> - The scope of the route. Possible values: <cf/SCOPE_HOST/ for routes - local to this host, <cf/SCOPE_LINK/ for those specific for a physical - link, <cf/SCOPE_SITE/ and <cf/SCOPE_ORGANIZATION/ for private routes and - <cf/SCOPE_UNIVERSE/ for globally visible routes. This attribute is not - interpreted by BIRD and can be used to mark routes in filters. The - default value for new routes is <cf/SCOPE_UNIVERSE/. - <tag><label id="rta-preference"><m/int/ preference</tag> - Preference of the route. Valid values are 0-65535. (See the chapter - about routing tables.) + Preference of the route. <tag><label id="rta-from"><m/ip/ from</tag> The router which the route has originated from. @@ -2097,6 +2187,13 @@ protocol bfd [<name>] { to configure separate BFD protocol instances for IPv4 and for IPv6 sessions. + <tag><label id="bfd-strict-bind">strict bind <m/switch/</tag> + Specify whether each BFD interface should use a separate listening + socket bound to its local address, or just use a shared listening socket + accepting all addresses. Binding to a specific address could be useful + in cases like running multiple BIRD instances on a machine, each + handling a different set of interfaces. Default: disabled. + <tag><label id="bfd-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag> Interface definitions allow to specify options for sessions associated with such interfaces and also may contain interface specific options. @@ -2281,6 +2378,7 @@ avoid routing loops. <item> <rfc id="8092"> - BGP Large Communities Attribute <item> <rfc id="8203"> - BGP Administrative Shutdown Communication <item> <rfc id="8212"> - Default EBGP Route Propagation Behavior without Policies +<item> <rfc id="9117"> - Revised Validation Procedure for BGP Flow Specifications </itemize> <sect1>Route selection rules @@ -2403,6 +2501,12 @@ using the following configuration parameters: same address family and using the same local port) should have set <cf/strict bind/, or none of them. Default: disabled. + <tag><label id="bgp-free-bind">free bind <m/switch/</tag> + Use IP_FREEBIND socket option for the listening socket, which allows + binding to an IP address not (yet) assigned to an interface. Note that + all BGP instances that share a listening socket should have the same + value of the <cf/freebind/ option. Default: disabled. + <tag><label id="bgp-check-link">check link <M>switch</M></tag> BGP could use hardware link state into consideration. If enabled, BIRD tracks the link state of the associated interface and when link @@ -2614,13 +2718,6 @@ using the following configuration parameters: disabled. Default: on, with automatic fallback to off when received capability-related error. - <tag><label id="bgp-advertise-ipv4">advertise ipv4 <m/switch/</tag> - Advertise IPv4 multiprotocol capability. This is not a correct behavior - according to the strict interpretation of <rfc id="4760">, but it is - widespread and required by some BGP implementations (Cisco and Quagga). - This option is relevant to IPv4 mode with enabled capability - advertisement only. Default: on. - <tag><label id="bgp-advertise-hostname">advertise hostname <m/switch/</tag> Advertise hostname capability along with the hostname. Default: off. @@ -2666,7 +2763,7 @@ using the following configuration parameters: <tag><label id="bgp-error-wait-time">error wait time <m/number/,<m/number/</tag> Minimum and maximum delay in seconds between a protocol failure (either - local or reported by the peer) and automatic restart. Doesn't apply + local or reported by the peer) and automatic restart. Doesn not apply when <cf/disable after error/ is configured. If consecutive errors happen, the delay is increased exponentially until it reaches the maximum. Default: 60, 300. @@ -2844,6 +2941,31 @@ be used in explicit configuration. explicitly (to conserve memory). This option requires that the connected routing table is <ref id="dsc-table-sorted" name="sorted">. Default: off. + <tag><label id="bgp-validate">validate <m/switch/</tag> + Apply flowspec validation procedure as described in <rfc id="8955"> + section 6 and <rfc id="9117">. The Validation procedure enforces that + only routers in the forwarding path for a network can originate flowspec + rules for that network. The validation procedure should be used for EBGP + to prevent injection of malicious flowspec rules from outside, but it + should also be used for IBGP to ensure that selected flowspec rules are + consistent with selected IP routes. The validation procedure uses an IP + routing table (<ref id="bgp-base-table" name="base table">, see below) + against which flowspec rules are validated. This option is limited to + flowspec channels. Default: off (for compatibility reasons). + + Note that currently the flowspec validation does not work reliably + together with <ref id="bgp-import-table" name="import table"> option + enabled on flowspec channels. + + <tag><label id="bgp-base-table">base table <m/name/</tag> + Specifies an IP table used for the flowspec validation procedure. The + table must have enabled <cf/trie/ option, otherwise the validation + procedure would not work. The type of the table must be <cf/ipv4/ for + <cf/flow4/ channels and <cf/ipv6/ for <cf/flow6/ channels. This option + is limited to flowspec channels. Default: the main table of the + <cf/ipv4/ / <cf/ipv6/ channel of the same BGP instance, or the + <cf/master4/ / <cf/master6/ table if there is no such channel. + <tag><label id="bgp-extended-next-hop">extended next hop <m/switch/</tag> BGP expects that announced next hops have the same address family as associated network prefixes. This option provides an extension to use @@ -3240,6 +3362,12 @@ channels. allows to specify a limit on maximal number of nexthops in one route. By default, multipath merging is disabled. If enabled, default value of the limit is 16. + + <tag><label id="krt-netlink-rx-buffer">netlink rx buffer <m/number/</tag> (Linux) + Set kernel receive buffer size (in bytes) for the netlink socket. The default + value is OS-dependent (from the <file>/proc/sys/net/core/rmem_default</file> + file), If you get some "Kernel dropped some netlink message ..." warnings, + you may increase this value. </descrip> <sect1>Attributes @@ -5165,7 +5293,7 @@ Note that for negated matches, value must be either zero or equal to bitmask <cf>port 1..1023,1194,3306</cf>). <tag><label id="flow-dport">dport <m/numbers-match/</tag> - Set a mating destination port numbers (e.g. <cf>dport 49151</cf>). + Set a matching destination port numbers (e.g. <cf>dport 49151</cf>). <tag><label id="flow-sport">sport <m/numbers-match/</tag> Set a matching source port numbers (e.g. <cf>sport = 0</cf>). @@ -5356,15 +5484,15 @@ name="atrey.karlin.mff.cuni.cz:/pub/rfc">). </book> <!-- -LocalWords: GPL IPv GateD BGPv RIPv OSPFv Linux sgml html dvi sgmltools Pavel +LocalWords: GPL IPv GateD BGPv RIPv OSPFv Linux sgml html dvi sgmltools LocalWords: linuxdoc dtd descrip config conf syslog stderr auth ospf bgp Mbps LocalWords: router's eval expr num birdc ctl UNIX if's enums bool int ip GCC LocalWords: len ipaddress pxlen netmask enum bgppath bgpmask clist gw md eth -LocalWords: RTS printn quitbird iBGP AS'es eBGP RFC multiprotocol IGP Machek +LocalWords: RTS printn quitbird iBGP AS'es eBGP RFC multiprotocol IGP LocalWords: EGP misconfigurations keepalive pref aggr aggregator BIRD's RTC LocalWords: OS'es AS's multicast nolisten misconfigured UID blackhole MRTD MTU LocalWords: uninstalls ethernets IP binutils ANYCAST anycast dest RTD ICMP rfc LocalWords: compat multicasts nonbroadcast pointopoint loopback sym stats LocalWords: Perl SIGHUP dd mm yy HH MM SS EXT IA UNICAST multihop Discriminator txt -LocalWords: proto wildcard Ondrej Filip +LocalWords: proto wildcard --> |