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Diffstat (limited to 'Documentation/networking/policy-routing.txt')
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diff --git a/Documentation/networking/policy-routing.txt b/Documentation/networking/policy-routing.txt deleted file mode 100644 index 36f6936d7f21..000000000000 --- a/Documentation/networking/policy-routing.txt +++ /dev/null @@ -1,150 +0,0 @@ -Classes -------- - - "Class" is a complete routing table in common sense. - I.e. it is tree of nodes (destination prefix, tos, metric) - with attached information: gateway, device etc. - This tree is looked up as specified in RFC1812 5.2.4.3 - 1. Basic match - 2. Longest match - 3. Weak TOS. - 4. Metric. (should not be in kernel space, but they are) - 5. Additional pruning rules. (not in kernel space). - - We have two special type of nodes: - REJECT - abort route lookup and return an error value. - THROW - abort route lookup in this class. - - - Currently the number of classes is limited to 255 - (0 is reserved for "not specified class") - - Three classes are builtin: - - RT_CLASS_LOCAL=255 - local interface addresses, - broadcasts, nat addresses. - - RT_CLASS_MAIN=254 - all normal routes are put there - by default. - - RT_CLASS_DEFAULT=253 - if ip_fib_model==1, then - normal default routes are put there, if ip_fib_model==2 - all gateway routes are put there. - - -Rules ------ - Rule is a record of (src prefix, src interface, tos, dst prefix) - with attached information. - - Rule types: - RTP_ROUTE - lookup in attached class - RTP_NAT - lookup in attached class and if a match is found, - translate packet source address. - RTP_MASQUERADE - lookup in attached class and if a match is found, - masquerade packet as sourced by us. - RTP_DROP - silently drop the packet. - RTP_REJECT - drop the packet and send ICMP NET UNREACHABLE. - RTP_PROHIBIT - drop the packet and send ICMP COMM. ADM. PROHIBITED. - - Rule flags: - RTRF_LOG - log route creations. - RTRF_VALVE - One way route (used with masquerading) - -Default setup: - -root@amber:/pub/ip-routing # iproute -r -Kernel routing policy rules -Pref Source Destination TOS Iface Cl - 0 default default 00 * 255 - 254 default default 00 * 254 - 255 default default 00 * 253 - - -Lookup algorithm ----------------- - - We scan rules list, and if a rule is matched, apply it. - If a route is found, return it. - If it is not found or a THROW node was matched, continue - to scan rules. - -Applications ------------- - -1. Just ignore classes. All the routes are put into MAIN class - (and/or into DEFAULT class). - - HOWTO: iproute add PREFIX [ tos TOS ] [ gw GW ] [ dev DEV ] - [ metric METRIC ] [ reject ] ... (look at iproute utility) - - or use route utility from current net-tools. - -2. Opposite case. Just forget all that you know about routing - tables. Every rule is supplied with its own gateway, device - info. record. This approach is not appropriate for automated - route maintenance, but it is ideal for manual configuration. - - HOWTO: iproute addrule [ from PREFIX ] [ to PREFIX ] [ tos TOS ] - [ dev INPUTDEV] [ pref PREFERENCE ] route [ gw GATEWAY ] - [ dev OUTDEV ] ..... - - Warning: As of now the size of the routing table in this - approach is limited to 256. If someone likes this model, I'll - relax this limitation. - -3. OSPF classes (see RFC1583, RFC1812 E.3.3) - Very clean, stable and robust algorithm for OSPF routing - domains. Unfortunately, it is not widely used in the Internet. - - Proposed setup: - 255 local addresses - 254 interface routes - 253 ASE routes with external metric - 252 ASE routes with internal metric - 251 inter-area routes - 250 intra-area routes for 1st area - 249 intra-area routes for 2nd area - etc. - - Rules: - iproute addrule class 253 - iproute addrule class 252 - iproute addrule class 251 - iproute addrule to a-prefix-for-1st-area class 250 - iproute addrule to another-prefix-for-1st-area class 250 - ... - iproute addrule to a-prefix-for-2nd-area class 249 - ... - - Area classes must be terminated with reject record. - iproute add default reject class 250 - iproute add default reject class 249 - ... - -4. The Variant Router Requirements Algorithm (RFC1812 E.3.2) - Create 16 classes for different TOS values. - It is a funny, but pretty useless algorithm. - I listed it just to show the power of new routing code. - -5. All the variety of combinations...... - - -GATED ------ - - Gated does not understand classes, but it will work - happily in MAIN+DEFAULT. All policy routes can be set - and maintained manually. - -IMPORTANT NOTE --------------- - route.c has a compilation time switch CONFIG_IP_LOCAL_RT_POLICY. - If it is set, locally originated packets are routed - using all the policy list. This is not very convenient and - pretty ambiguous when used with NAT and masquerading. - I set it to FALSE by default. - - -Alexey Kuznetov -kuznet@ms2.inr.ac.ru |