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31 L3 Forwarding with Access Control Sample Application
32 ====================================================
34 The L3 Forwarding with Access Control application is a simple example of packet processing using the DPDK.
35 The application performs a security check on received packets.
36 Packets that are in the Access Control List (ACL), which is loaded during initialization, are dropped.
37 Others are forwarded to the correct port.
42 The application demonstrates the use of the ACL library in the DPDK to implement access control
43 and packet L3 forwarding.
44 The application loads two types of rules at initialization:
46 * Route information rules, which are used for L3 forwarding
48 * Access Control List (ACL) rules that blacklist (or block) packets with a specific characteristic
50 When packets are received from a port,
51 the application extracts the necessary information from the TCP/IP header of the received packet and
52 performs a lookup in the rule database to figure out whether the packets should be dropped (in the ACL range)
53 or forwarded to desired ports.
54 The initialization and run-time paths are similar to those of the :doc:`l3_forward`.
55 However, there are significant differences in the two applications.
56 For example, the original L3 forwarding application uses either LPM or
57 an exact match algorithm to perform forwarding port lookup,
58 while this application uses the ACL library to perform both ACL and route entry lookup.
59 The following sections provide more detail.
61 Classification for both IPv4 and IPv6 packets is supported in this application.
62 The application also assumes that all the packets it processes are TCP/UDP packets and
63 always extracts source/destination port information from the packets.
68 The application implements packet classification for the IPv4/IPv6 5-tuple syntax specifically.
69 The 5-tuple syntax consist of a source IP address, a destination IP address,
70 a source port, a destination port and a protocol identifier.
71 The fields in the 5-tuple syntax have the following formats:
73 * **Source IP address and destination IP address**
74 : Each is either a 32-bit field (for IPv4), or a set of 4 32-bit fields (for IPv6) represented by a value and a mask length.
75 For example, an IPv4 range of 192.168.1.0 to 192.168.1.255 could be represented by a value = [192, 168, 1, 0] and a mask length = 24.
77 * **Source port and destination port**
78 : Each is a 16-bit field, represented by a lower start and a higher end.
79 For example, a range of ports 0 to 8192 could be represented by lower = 0 and higher = 8192.
81 * **Protocol identifier**
82 : An 8-bit field, represented by a value and a mask, that covers a range of values.
83 To verify that a value is in the range, use the following expression: "(VAL & mask) == value"
85 The trick in how to represent a range with a mask and value is as follows.
86 A range can be enumerated in binary numbers with some bits that are never changed and some bits that are dynamically changed.
87 Set those bits that dynamically changed in mask and value with 0.
88 Set those bits that never changed in the mask with 1, in value with number expected.
89 For example, a range of 6 to 7 is enumerated as 0b110 and 0b111.
90 Bit 1-7 are bits never changed and bit 0 is the bit dynamically changed.
91 Therefore, set bit 0 in mask and value with 0, set bits 1-7 in mask with 1, and bits 1-7 in value with number 0b11.
92 So, mask is 0xfe, value is 0x6.
96 The library assumes that each field in the rule is in LSB or Little Endian order when creating the database.
97 It internally converts them to MSB or Big Endian order.
98 When performing a lookup, the library assumes the input is in MSB or Big Endian order.
103 In this sample application, each rule is a combination of the following:
105 * 5-tuple field: This field has a format described in Section.
107 * priority field: A weight to measure the priority of the rules.
108 The rule with the higher priority will ALWAYS be returned if the specific input has multiple matches in the rule database.
109 Rules with lower priority will NEVER be returned in any cases.
111 * userdata field: A user-defined field that could be any value.
112 It can be the forwarding port number if the rule is a route table entry or it can be a pointer to a mapping address
113 if the rule is used for address mapping in the NAT application.
114 The key point is that it is a useful reserved field for user convenience.
119 The application needs to acquire ACL and route rules before it runs.
120 Route rules are mandatory, while ACL rules are optional.
121 To simplify the complexity of the priority field for each rule, all ACL and route entries are assumed to be in the same file.
122 To read data from the specified file successfully, the application assumes the following:
124 * Each rule occupies a single line.
126 * Only the following four rule line types are valid in this application:
128 * ACL rule line, which starts with a leading character '@'
130 * Route rule line, which starts with a leading character 'R'
132 * Comment line, which starts with a leading character '#'
134 * Empty line, which consists of a space, form-feed ('\f'), newline ('\n'),
135 carriage return ('\r'), horizontal tab ('\t'), or vertical tab ('\v').
137 Other lines types are considered invalid.
139 * Rules are organized in descending order of priority,
140 which means rules at the head of the file always have a higher priority than those further down in the file.
142 * A typical IPv4 ACL rule line should have a format as shown below:
145 .. _figure_ipv4_acl_rule:
147 .. figure:: img/ipv4_acl_rule.*
149 A typical IPv4 ACL rule
152 IPv4 addresses are specified in CIDR format as specified in RFC 4632.
153 They consist of the dot notation for the address and a prefix length separated by '/'.
154 For example, 192.168.0.34/32, where the address is 192.168.0.34 and the prefix length is 32.
156 Ports are specified as a range of 16-bit numbers in the format MIN:MAX,
157 where MIN and MAX are the inclusive minimum and maximum values of the range.
158 The range 0:65535 represents all possible ports in a range.
159 When MIN and MAX are the same value, a single port is represented, for example, 20:20.
161 The protocol identifier is an 8-bit value and a mask separated by '/'.
162 For example: 6/0xfe matches protocol values 6 and 7.
164 * Route rules start with a leading character 'R' and have the same format as ACL rules except an extra field at the tail
165 that indicates the forwarding port number.
170 .. _figure_example_rules:
172 .. figure:: img/example_rules.*
177 Each rule is explained as follows:
179 * Rule 1 (the first line) tells the application to drop those packets with source IP address = [1.2.3.*],
180 destination IP address = [192.168.0.36], protocol = [6]/[7]
182 * Rule 2 (the second line) is similar to Rule 1, except the source IP address is ignored.
183 It tells the application to forward packets with destination IP address = [192.168.0.36],
184 protocol = [6]/[7], destined to port 1.
186 * Rule 3 (the third line) tells the application to forward all packets to port 0.
187 This is something like a default route entry.
189 As described earlier, the application assume rules are listed in descending order of priority,
190 therefore Rule 1 has the highest priority, then Rule 2, and finally,
191 Rule 3 has the lowest priority.
193 Consider the arrival of the following three packets:
195 * Packet 1 has source IP address = [1.2.3.4], destination IP address = [192.168.0.36], and protocol = [6]
197 * Packet 2 has source IP address = [1.2.4.4], destination IP address = [192.168.0.36], and protocol = [6]
199 * Packet 3 has source IP address = [1.2.3.4], destination IP address = [192.168.0.36], and protocol = [8]
203 * Packet 1 matches all of the rules
205 * Packet 2 matches Rule 2 and Rule 3
207 * Packet 3 only matches Rule 3
209 For priority reasons, Packet 1 matches Rule 1 and is dropped.
210 Packet 2 matches Rule 2 and is forwarded to port 1.
211 Packet 3 matches Rule 3 and is forwarded to port 0.
213 For more details on the rule file format,
214 please refer to rule_ipv4.db and rule_ipv6.db files (inside <RTE_SDK>/examples/l3fwd-acl/).
219 Once the application starts, it transitions through three phases:
221 * **Initialization Phase**
222 - Perform the following tasks:
224 * Parse command parameters. Check the validity of rule file(s) name(s), number of logical cores, receive and transmit queues.
225 Bind ports, queues and logical cores. Check ACL search options, and so on.
227 * Call Environmental Abstraction Layer (EAL) and Poll Mode Driver (PMD) functions to initialize the environment and detect possible NICs.
228 The EAL creates several threads and sets affinity to a specific hardware thread CPU based on the configuration specified
229 by the command line arguments.
231 * Read the rule files and format the rules into the representation that the ACL library can recognize.
232 Call the ACL library function to add the rules into the database and compile them as a trie of pattern sets.
233 Note that application maintains a separate AC contexts for IPv4 and IPv6 rules.
236 - Process the incoming packets from a port. Packets are processed in three steps:
238 * Retrieval: Gets a packet from the receive queue. Each logical core may process several queues for different ports.
239 This depends on the configuration specified by command line arguments.
241 * Lookup: Checks that the packet type is supported (IPv4/IPv6) and performs a 5-tuple lookup over corresponding AC context.
242 If an ACL rule is matched, the packets will be dropped and return back to step 1.
243 If a route rule is matched, it indicates the packet is not in the ACL list and should be forwarded.
244 If there is no matches for the packet, then the packet is dropped.
246 * Forwarding: Forwards the packet to the corresponding port.
248 * **Final Phase** - Perform the following tasks:
250 Calls the EAL, PMD driver and ACL library to free resource, then quits.
252 Compiling the Application
253 -------------------------
255 To compile the application:
257 #. Go to the sample application directory:
259 .. code-block:: console
261 export RTE_SDK=/path/to/rte_sdk
262 cd ${RTE_SDK}/examples/l3fwd-acl
264 #. Set the target (a default target is used if not specified). For example:
266 .. code-block:: console
268 export RTE_TARGET=x86_64-native-linuxapp-gcc
270 See the *DPDK IPL Getting Started Guide* for possible RTE_TARGET values.
272 #. Build the application:
274 .. code-block:: console
278 Running the Application
279 -----------------------
281 The application has a number of command line options:
283 .. code-block:: console
285 ./build/l3fwd-acl [EAL options] -- -p PORTMASK [-P] --config(port,queue,lcore)[,(port,queue,lcore)] --rule_ipv4 FILENAME rule_ipv6 FILENAME [--scalar] [--enable-jumbo [--max-pkt-len PKTLEN]] [--no-numa]
290 * -p PORTMASK: Hexadecimal bitmask of ports to configure
292 * -P: Sets all ports to promiscuous mode so that packets are accepted regardless of the packet's Ethernet MAC destination address.
293 Without this option, only packets with the Ethernet MAC destination address set to the Ethernet address of the port are accepted.
295 * --config (port,queue,lcore)[,(port,queue,lcore)]: determines which queues from which ports are mapped to which cores
297 * --rule_ipv4 FILENAME: Specifies the IPv4 ACL and route rules file
299 * --rule_ipv6 FILENAME: Specifies the IPv6 ACL and route rules file
301 * --scalar: Use a scalar function to perform rule lookup
303 * --enable-jumbo: optional, enables jumbo frames
305 * --max-pkt-len: optional, maximum packet length in decimal (64-9600)
307 * --no-numa: optional, disables numa awareness
309 For example, consider a dual processor socket platform with 8 physical cores, where cores 0-7 and 16-23 appear on socket 0,
310 while cores 8-15 and 24-31 appear on socket 1.
312 To enable L3 forwarding between two ports, assuming that both ports are in the same socket, using two cores, cores 1 and 2,
313 (which are in the same socket too), use the following command:
315 .. code-block:: console
317 ./build/l3fwd-acl -l 1,2 -n 4 -- -p 0x3 --config="(0,0,1),(1,0,2)" --rule_ipv4="./rule_ipv4.db" -- rule_ipv6="./rule_ipv6.db" --scalar
321 * The -l option enables cores 1, 2
323 * The -p option enables ports 0 and 1
325 * The --config option enables one queue on each port and maps each (port,queue) pair to a specific core.
326 The following table shows the mapping in this example:
328 +----------+------------+-----------+-------------------------------------+
329 | **Port** | **Queue** | **lcore** | **Description** |
331 +==========+============+===========+=====================================+
332 | 0 | 0 | 1 | Map queue 0 from port 0 to lcore 1. |
334 +----------+------------+-----------+-------------------------------------+
335 | 1 | 0 | 2 | Map queue 0 from port 1 to lcore 2. |
337 +----------+------------+-----------+-------------------------------------+
339 * The --rule_ipv4 option specifies the reading of IPv4 rules sets from the ./ rule_ipv4.db file.
341 * The --rule_ipv6 option specifies the reading of IPv6 rules sets from the ./ rule_ipv6.db file.
343 * The --scalar option specifies the performing of rule lookup with a scalar function.
348 The following sections provide some explanation of the sample application code.
349 The aspects of port, device and CPU configuration are similar to those of the :doc:`l3_forward`.
350 The following sections describe aspects that are specific to L3 forwarding with access control.
352 Parse Rules from File
353 ~~~~~~~~~~~~~~~~~~~~~
355 As described earlier, both ACL and route rules are assumed to be saved in the same file.
356 The application parses the rules from the file and adds them to the database by calling the ACL library function.
357 It ignores empty and comment lines, and parses and validates the rules it reads.
358 If errors are detected, the application exits with messages to identify the errors encountered.
360 The application needs to consider the userdata and priority fields.
361 The ACL rules save the index to the specific rules in the userdata field,
362 while route rules save the forwarding port number.
363 In order to differentiate the two types of rules, ACL rules add a signature in the userdata field.
364 As for the priority field, the application assumes rules are organized in descending order of priority.
365 Therefore, the code only decreases the priority number with each rule it parses.
367 Setting Up the ACL Context
368 ~~~~~~~~~~~~~~~~~~~~~~~~~~
370 For each supported AC rule format (IPv4 5-tuple, IPv6 6-tuple) application creates a separate context handler
371 from the ACL library for each CPU socket on the board and adds parsed rules into that context.
373 Note, that for each supported rule type,
374 application needs to calculate the expected offset of the fields from the start of the packet.
375 That's why only packets with fixed IPv4/ IPv6 header are supported.
376 That allows to perform ACL classify straight over incoming packet buffer -
377 no extra protocol field retrieval need to be performed.
379 Subsequently, the application checks whether NUMA is enabled.
380 If it is, the application records the socket IDs of the CPU cores involved in the task.
382 Finally, the application creates contexts handler from the ACL library,
383 adds rules parsed from the file into the database and build an ACL trie.
384 It is important to note that the application creates an independent copy of each database for each socket CPU
385 involved in the task to reduce the time for remote memory access.