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31 L3 Forwarding Sample Application
32 ================================
34 The L3 Forwarding application is a simple example of packet processing using the DPDK.
35 The application performs L3 forwarding.
40 The application demonstrates the use of the hash and LPM libraries in the DPDK to implement packet forwarding.
41 The initialization and run-time paths are very similar to those of the :doc:`l2_forward_real_virtual`.
42 The main difference from the L2 Forwarding sample application is that the forwarding decision
43 is made based on information read from the input packet.
45 The lookup method is either hash-based or LPM-based and is selected at compile time. When the selected lookup method is hash-based,
46 a hash object is used to emulate the flow classification stage.
47 The hash object is used in correlation with a flow table to map each input packet to its flow at runtime.
49 The hash lookup key is represented by a DiffServ 5-tuple composed of the following fields read from the input packet:
50 Source IP Address, Destination IP Address, Protocol, Source Port and Destination Port.
51 The ID of the output interface for the input packet is read from the identified flow table entry.
52 The set of flows used by the application is statically configured and loaded into the hash at initialization time.
53 When the selected lookup method is LPM based, an LPM object is used to emulate the forwarding stage for IPv4 packets.
54 The LPM object is used as the routing table to identify the next hop for each input packet at runtime.
56 The LPM lookup key is represented by the Destination IP Address field read from the input packet.
57 The ID of the output interface for the input packet is the next hop returned by the LPM lookup.
58 The set of LPM rules used by the application is statically configured and loaded into the LPM object at initialization time.
60 In the sample application, hash-based forwarding supports IPv4 and IPv6. LPM-based forwarding supports IPv4 only.
62 Compiling the Application
63 -------------------------
65 To compile the application:
67 #. Go to the sample application directory:
69 .. code-block:: console
71 export RTE_SDK=/path/to/rte_sdk
72 cd ${RTE_SDK}/examples/l3fwd
74 #. Set the target (a default target is used if not specified). For example:
76 .. code-block:: console
78 export RTE_TARGET=x86_64-native-linuxapp-gcc
80 See the *DPDK Getting Started Guide* for possible RTE_TARGET values.
82 #. Build the application:
84 .. code-block:: console
88 Running the Application
89 -----------------------
91 The application has a number of command line options:
93 .. code-block:: console
95 ./build/l3fwd [EAL options] -- -p PORTMASK [-P] --config(port,queue,lcore)[,(port,queue,lcore)] [--enable-jumbo [--max-pkt-len PKTLEN]] [--no-numa][--hash-entry-num][--ipv6]
99 * -p PORTMASK: Hexadecimal bitmask of ports to configure
101 * -P: optional, sets all ports to promiscuous mode so that packets are accepted regardless of the packet's Ethernet MAC destination address.
102 Without this option, only packets with the Ethernet MAC destination address set to the Ethernet address of the port are accepted.
104 * --config (port,queue,lcore)[,(port,queue,lcore)]: determines which queues from which ports are mapped to which cores
106 * --enable-jumbo: optional, enables jumbo frames
108 * --max-pkt-len: optional, maximum packet length in decimal (64-9600)
110 * --no-numa: optional, disables numa awareness
112 * --hash-entry-num: optional, specifies the hash entry number in hexadecimal to be setup
114 * --ipv6: optional, set it if running ipv6 packets
116 For example, consider a dual processor socket platform where cores 0-7 and 16-23 appear on socket 0, while cores 8-15 and 24-31 appear on socket 1.
117 Let's say that the programmer wants to use memory from both NUMA nodes, the platform has only two ports, one connected to each NUMA node,
118 and the programmer wants to use two cores from each processor socket to do the packet processing.
120 To enable L3 forwarding between two ports, using two cores, cores 1 and 2, from each processor,
121 while also taking advantage of local memory access by optimizing around NUMA, the programmer must enable two queues from each port,
122 pin to the appropriate cores and allocate memory from the appropriate NUMA node. This is achieved using the following command:
124 .. code-block:: console
126 ./build/l3fwd -c 606 -n 4 -- -p 0x3 --config="(0,0,1),(0,1,2),(1,0,9),(1,1,10)"
130 * The -c option enables cores 0, 1, 2, 3
132 * The -p option enables ports 0 and 1
134 * The --config option enables two queues on each port and maps each (port,queue) pair to a specific core.
135 Logic to enable multiple RX queues using RSS and to allocate memory from the correct NUMA nodes
136 is included in the application and is done transparently.
137 The following table shows the mapping in this example:
139 +----------+-----------+-----------+-------------------------------------+
140 | **Port** | **Queue** | **lcore** | **Description** |
142 +----------+-----------+-----------+-------------------------------------+
143 | 0 | 0 | 0 | Map queue 0 from port 0 to lcore 0. |
145 +----------+-----------+-----------+-------------------------------------+
146 | 0 | 1 | 2 | Map queue 1 from port 0 to lcore 2. |
148 +----------+-----------+-----------+-------------------------------------+
149 | 1 | 0 | 1 | Map queue 0 from port 1 to lcore 1. |
151 +----------+-----------+-----------+-------------------------------------+
152 | 1 | 1 | 3 | Map queue 1 from port 1 to lcore 3. |
154 +----------+-----------+-----------+-------------------------------------+
156 Refer to the *DPDK Getting Started Guide* for general information on running applications and
157 the Environment Abstraction Layer (EAL) options.
159 .. _l3_fwd_explanation:
164 The following sections provide some explanation of the sample application code. As mentioned in the overview section,
165 the initialization and run-time paths are very similar to those of the :doc:`l2_forward_real_virtual`.
166 The following sections describe aspects that are specific to the L3 Forwarding sample application.
171 The hash object is created and loaded with the pre-configured entries read from a global array,
172 and then generate the expected 5-tuple as key to keep consistence with those of real flow
173 for the convenience to execute hash performance test on 4M/8M/16M flows.
177 The Hash initialization will setup both ipv4 and ipv6 hash table,
178 and populate the either table depending on the value of variable ipv6.
179 To support the hash performance test with up to 8M single direction flows/16M bi-direction flows,
180 populate_ipv4_many_flow_into_table() function will populate the hash table with specified hash table entry number(default 4M).
184 Value of global variable ipv6 can be specified with --ipv6 in the command line.
185 Value of global variable hash_entry_number,
186 which is used to specify the total hash entry number for all used ports in hash performance test,
187 can be specified with --hash-entry-num VALUE in command line, being its default value 4.
191 #if (APP_LOOKUP_METHOD == APP_LOOKUP_EXACT_MATCH)
194 setup_hash(int socketid)
198 if (hash_entry_number != HASH_ENTRY_NUMBER_DEFAULT) {
200 /* populate the ipv4 hash */
201 populate_ipv4_many_flow_into_table(ipv4_l3fwd_lookup_struct[socketid], hash_entry_number);
203 /* populate the ipv6 hash */
204 populate_ipv6_many_flow_into_table( ipv6_l3fwd_lookup_struct[socketid], hash_entry_number);
208 /* populate the ipv4 hash */
209 populate_ipv4_few_flow_into_table(ipv4_l3fwd_lookup_struct[socketid]);
211 /* populate the ipv6 hash */
212 populate_ipv6_few_flow_into_table(ipv6_l3fwd_lookup_struct[socketid]);
221 The LPM object is created and loaded with the pre-configured entries read from a global array.
225 #if (APP_LOOKUP_METHOD == APP_LOOKUP_LPM)
228 setup_lpm(int socketid)
234 /* create the LPM table */
236 snprintf(s, sizeof(s), "IPV4_L3FWD_LPM_%d", socketid);
238 ipv4_l3fwd_lookup_struct[socketid] = rte_lpm_create(s, socketid, IPV4_L3FWD_LPM_MAX_RULES, 0);
240 if (ipv4_l3fwd_lookup_struct[socketid] == NULL)
241 rte_exit(EXIT_FAILURE, "Unable to create the l3fwd LPM table"
242 " on socket %d\n", socketid);
244 /* populate the LPM table */
246 for (i = 0; i < IPV4_L3FWD_NUM_ROUTES; i++) {
247 /* skip unused ports */
249 if ((1 << ipv4_l3fwd_route_array[i].if_out & enabled_port_mask) == 0)
252 ret = rte_lpm_add(ipv4_l3fwd_lookup_struct[socketid], ipv4_l3fwd_route_array[i].ip,
253 ipv4_l3fwd_route_array[i].depth, ipv4_l3fwd_route_array[i].if_out);
256 rte_exit(EXIT_FAILURE, "Unable to add entry %u to the "
257 "l3fwd LPM table on socket %d\n", i, socketid);
260 printf("LPM: Adding route 0x%08x / %d (%d)\n",
261 (unsigned)ipv4_l3fwd_route_array[i].ip, ipv4_l3fwd_route_array[i].depth, ipv4_l3fwd_route_array[i].if_out);
266 Packet Forwarding for Hash-based Lookups
267 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
269 For each input packet, the packet forwarding operation is done by the l3fwd_simple_forward()
270 or simple_ipv4_fwd_4pkts() function for IPv4 packets or the simple_ipv6_fwd_4pkts() function for IPv6 packets.
271 The l3fwd_simple_forward() function provides the basic functionality for both IPv4 and IPv6 packet forwarding
272 for any number of burst packets received,
273 and the packet forwarding decision (that is, the identification of the output interface for the packet)
274 for hash-based lookups is done by the get_ipv4_dst_port() or get_ipv6_dst_port() function.
275 The get_ipv4_dst_port() function is shown below:
279 static inline uint8_t
280 get_ipv4_dst_port(void *ipv4_hdr, uint8_t portid, lookup_struct_t *ipv4_l3fwd_lookup_struct)
283 union ipv4_5tuple_host key;
285 ipv4_hdr = (uint8_t \*)ipv4_hdr + offsetof(struct ipv4_hdr, time_to_live);
287 m128i data = _mm_loadu_si128(( m128i*)(ipv4_hdr));
289 /* Get 5 tuple: dst port, src port, dst IP address, src IP address and protocol */
291 key.xmm = _mm_and_si128(data, mask0);
293 /* Find destination port */
295 ret = rte_hash_lookup(ipv4_l3fwd_lookup_struct, (const void *)&key);
297 return (uint8_t)((ret < 0)? portid : ipv4_l3fwd_out_if[ret]);
300 The get_ipv6_dst_port() function is similar to the get_ipv4_dst_port() function.
302 The simple_ipv4_fwd_4pkts() and simple_ipv6_fwd_4pkts() function are optimized for continuous 4 valid ipv4 and ipv6 packets,
303 they leverage the multiple buffer optimization to boost the performance of forwarding packets with the exact match on hash table.
304 The key code snippet of simple_ipv4_fwd_4pkts() is shown below:
309 simple_ipv4_fwd_4pkts(struct rte_mbuf* m[4], uint8_t portid, struct lcore_conf *qconf)
313 data[0] = _mm_loadu_si128(( m128i*)(rte_pktmbuf_mtod(m[0], unsigned char *) + sizeof(struct ether_hdr) + offsetof(struct ipv4_hdr, time_to_live)));
314 data[1] = _mm_loadu_si128(( m128i*)(rte_pktmbuf_mtod(m[1], unsigned char *) + sizeof(struct ether_hdr) + offsetof(struct ipv4_hdr, time_to_live)));
315 data[2] = _mm_loadu_si128(( m128i*)(rte_pktmbuf_mtod(m[2], unsigned char *) + sizeof(struct ether_hdr) + offsetof(struct ipv4_hdr, time_to_live)));
316 data[3] = _mm_loadu_si128(( m128i*)(rte_pktmbuf_mtod(m[3], unsigned char *) + sizeof(struct ether_hdr) + offsetof(struct ipv4_hdr, time_to_live)));
318 key[0].xmm = _mm_and_si128(data[0], mask0);
319 key[1].xmm = _mm_and_si128(data[1], mask0);
320 key[2].xmm = _mm_and_si128(data[2], mask0);
321 key[3].xmm = _mm_and_si128(data[3], mask0);
323 const void *key_array[4] = {&key[0], &key[1], &key[2],&key[3]};
325 rte_hash_lookup_multi(qconf->ipv4_lookup_struct, &key_array[0], 4, ret);
327 dst_port[0] = (ret[0] < 0)? portid:ipv4_l3fwd_out_if[ret[0]];
328 dst_port[1] = (ret[1] < 0)? portid:ipv4_l3fwd_out_if[ret[1]];
329 dst_port[2] = (ret[2] < 0)? portid:ipv4_l3fwd_out_if[ret[2]];
330 dst_port[3] = (ret[3] < 0)? portid:ipv4_l3fwd_out_if[ret[3]];
335 The simple_ipv6_fwd_4pkts() function is similar to the simple_ipv4_fwd_4pkts() function.
337 Packet Forwarding for LPM-based Lookups
338 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
340 For each input packet, the packet forwarding operation is done by the l3fwd_simple_forward() function,
341 but the packet forwarding decision (that is, the identification of the output interface for the packet)
342 for LPM-based lookups is done by the get_ipv4_dst_port() function below:
346 static inline uint8_t
347 get_ipv4_dst_port(struct ipv4_hdr *ipv4_hdr, uint8_t portid, lookup_struct_t *ipv4_l3fwd_lookup_struct)
351 return (uint8_t) ((rte_lpm_lookup(ipv4_l3fwd_lookup_struct, rte_be_to_cpu_32(ipv4_hdr->dst_addr), &next_hop) == 0)? next_hop : portid);