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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 run 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 sample application see :doc:`compiling`.
67 The application is located in the ``l3fwd`` sub-directory.
69 Running the Application
70 -----------------------
72 The application has a number of command line options::
74 ./l3fwd [EAL options] -- -p PORTMASK
78 --config(port,queue,lcore)[,(port,queue,lcore)]
79 [--eth-dest=X,MM:MM:MM:MM:MM:MM]
80 [--enable-jumbo [--max-pkt-len PKTLEN]]
88 * ``-p PORTMASK:`` Hexadecimal bitmask of ports to configure
90 * ``-P:`` Optional, sets all ports to promiscuous mode so that packets are accepted regardless of the packet's Ethernet MAC destination address.
91 Without this option, only packets with the Ethernet MAC destination address set to the Ethernet address of the port are accepted.
93 * ``-E:`` Optional, enable exact match.
95 * ``-L:`` Optional, enable longest prefix match.
97 * ``--config (port,queue,lcore)[,(port,queue,lcore)]:`` Determines which queues from which ports are mapped to which cores.
99 * ``--eth-dest=X,MM:MM:MM:MM:MM:MM:`` Optional, ethernet destination for port X.
101 * ``--enable-jumbo:`` Optional, enables jumbo frames.
103 * ``--max-pkt-len:`` Optional, under the premise of enabling jumbo, maximum packet length in decimal (64-9600).
105 * ``--no-numa:`` Optional, disables numa awareness.
107 * ``--hash-entry-num:`` Optional, specifies the hash entry number in hexadecimal to be setup.
109 * ``--ipv6:`` Optional, set if running ipv6 packets.
111 * ``--parse-ptype:`` Optional, set to use software to analyze packet type. Without this option, hardware will check the packet type.
113 For example, consider a dual processor socket platform with 8 physical cores, where cores 0-7 and 16-23 appear on socket 0,
114 while cores 8-15 and 24-31 appear on socket 1.
116 To enable L3 forwarding between two ports, assuming that both ports are in the same socket, using two cores, cores 1 and 2,
117 (which are in the same socket too), use the following command:
119 .. code-block:: console
121 ./build/l3fwd -l 1,2 -n 4 -- -p 0x3 --config="(0,0,1),(1,0,2)"
125 * The -l option enables cores 1, 2
127 * The -p option enables ports 0 and 1
129 * The --config option enables one queue on each port and maps each (port,queue) pair to a specific core.
130 The following table shows the mapping in this example:
132 +----------+-----------+-----------+-------------------------------------+
133 | **Port** | **Queue** | **lcore** | **Description** |
135 +----------+-----------+-----------+-------------------------------------+
136 | 0 | 0 | 1 | Map queue 0 from port 0 to lcore 1. |
138 +----------+-----------+-----------+-------------------------------------+
139 | 1 | 0 | 2 | Map queue 0 from port 1 to lcore 2. |
141 +----------+-----------+-----------+-------------------------------------+
143 Refer to the *DPDK Getting Started Guide* for general information on running applications and
144 the Environment Abstraction Layer (EAL) options.
146 .. _l3_fwd_explanation:
151 The following sections provide some explanation of the sample application code. As mentioned in the overview section,
152 the initialization and run-time paths are very similar to those of the :doc:`l2_forward_real_virtual`.
153 The following sections describe aspects that are specific to the L3 Forwarding sample application.
158 The hash object is created and loaded with the pre-configured entries read from a global array,
159 and then generate the expected 5-tuple as key to keep consistence with those of real flow
160 for the convenience to execute hash performance test on 4M/8M/16M flows.
164 The Hash initialization will setup both ipv4 and ipv6 hash table,
165 and populate the either table depending on the value of variable ipv6.
166 To support the hash performance test with up to 8M single direction flows/16M bi-direction flows,
167 populate_ipv4_many_flow_into_table() function will populate the hash table with specified hash table entry number(default 4M).
171 Value of global variable ipv6 can be specified with --ipv6 in the command line.
172 Value of global variable hash_entry_number,
173 which is used to specify the total hash entry number for all used ports in hash performance test,
174 can be specified with --hash-entry-num VALUE in command line, being its default value 4.
178 #if (APP_LOOKUP_METHOD == APP_LOOKUP_EXACT_MATCH)
181 setup_hash(int socketid)
185 if (hash_entry_number != HASH_ENTRY_NUMBER_DEFAULT) {
187 /* populate the ipv4 hash */
188 populate_ipv4_many_flow_into_table(ipv4_l3fwd_lookup_struct[socketid], hash_entry_number);
190 /* populate the ipv6 hash */
191 populate_ipv6_many_flow_into_table( ipv6_l3fwd_lookup_struct[socketid], hash_entry_number);
195 /* populate the ipv4 hash */
196 populate_ipv4_few_flow_into_table(ipv4_l3fwd_lookup_struct[socketid]);
198 /* populate the ipv6 hash */
199 populate_ipv6_few_flow_into_table(ipv6_l3fwd_lookup_struct[socketid]);
208 The LPM object is created and loaded with the pre-configured entries read from a global array.
212 #if (APP_LOOKUP_METHOD == APP_LOOKUP_LPM)
215 setup_lpm(int socketid)
221 /* create the LPM table */
223 snprintf(s, sizeof(s), "IPV4_L3FWD_LPM_%d", socketid);
225 ipv4_l3fwd_lookup_struct[socketid] = rte_lpm_create(s, socketid, IPV4_L3FWD_LPM_MAX_RULES, 0);
227 if (ipv4_l3fwd_lookup_struct[socketid] == NULL)
228 rte_exit(EXIT_FAILURE, "Unable to create the l3fwd LPM table"
229 " on socket %d\n", socketid);
231 /* populate the LPM table */
233 for (i = 0; i < IPV4_L3FWD_NUM_ROUTES; i++) {
234 /* skip unused ports */
236 if ((1 << ipv4_l3fwd_route_array[i].if_out & enabled_port_mask) == 0)
239 ret = rte_lpm_add(ipv4_l3fwd_lookup_struct[socketid], ipv4_l3fwd_route_array[i].ip,
240 ipv4_l3fwd_route_array[i].depth, ipv4_l3fwd_route_array[i].if_out);
243 rte_exit(EXIT_FAILURE, "Unable to add entry %u to the "
244 "l3fwd LPM table on socket %d\n", i, socketid);
247 printf("LPM: Adding route 0x%08x / %d (%d)\n",
248 (unsigned)ipv4_l3fwd_route_array[i].ip, ipv4_l3fwd_route_array[i].depth, ipv4_l3fwd_route_array[i].if_out);
253 Packet Forwarding for Hash-based Lookups
254 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
256 For each input packet, the packet forwarding operation is done by the l3fwd_simple_forward()
257 or simple_ipv4_fwd_4pkts() function for IPv4 packets or the simple_ipv6_fwd_4pkts() function for IPv6 packets.
258 The l3fwd_simple_forward() function provides the basic functionality for both IPv4 and IPv6 packet forwarding
259 for any number of burst packets received,
260 and the packet forwarding decision (that is, the identification of the output interface for the packet)
261 for hash-based lookups is done by the get_ipv4_dst_port() or get_ipv6_dst_port() function.
262 The get_ipv4_dst_port() function is shown below:
266 static inline uint8_t
267 get_ipv4_dst_port(void *ipv4_hdr, uint16_t portid, lookup_struct_t *ipv4_l3fwd_lookup_struct)
270 union ipv4_5tuple_host key;
272 ipv4_hdr = (uint8_t *)ipv4_hdr + offsetof(struct ipv4_hdr, time_to_live);
274 m128i data = _mm_loadu_si128(( m128i*)(ipv4_hdr));
276 /* Get 5 tuple: dst port, src port, dst IP address, src IP address and protocol */
278 key.xmm = _mm_and_si128(data, mask0);
280 /* Find destination port */
282 ret = rte_hash_lookup(ipv4_l3fwd_lookup_struct, (const void *)&key);
284 return (uint8_t)((ret < 0)? portid : ipv4_l3fwd_out_if[ret]);
287 The get_ipv6_dst_port() function is similar to the get_ipv4_dst_port() function.
289 The simple_ipv4_fwd_4pkts() and simple_ipv6_fwd_4pkts() function are optimized for continuous 4 valid ipv4 and ipv6 packets,
290 they leverage the multiple buffer optimization to boost the performance of forwarding packets with the exact match on hash table.
291 The key code snippet of simple_ipv4_fwd_4pkts() is shown below:
296 simple_ipv4_fwd_4pkts(struct rte_mbuf* m[4], uint16_t portid, struct lcore_conf *qconf)
300 data[0] = _mm_loadu_si128(( m128i*)(rte_pktmbuf_mtod(m[0], unsigned char *) + sizeof(struct ether_hdr) + offsetof(struct ipv4_hdr, time_to_live)));
301 data[1] = _mm_loadu_si128(( m128i*)(rte_pktmbuf_mtod(m[1], unsigned char *) + sizeof(struct ether_hdr) + offsetof(struct ipv4_hdr, time_to_live)));
302 data[2] = _mm_loadu_si128(( m128i*)(rte_pktmbuf_mtod(m[2], unsigned char *) + sizeof(struct ether_hdr) + offsetof(struct ipv4_hdr, time_to_live)));
303 data[3] = _mm_loadu_si128(( m128i*)(rte_pktmbuf_mtod(m[3], unsigned char *) + sizeof(struct ether_hdr) + offsetof(struct ipv4_hdr, time_to_live)));
305 key[0].xmm = _mm_and_si128(data[0], mask0);
306 key[1].xmm = _mm_and_si128(data[1], mask0);
307 key[2].xmm = _mm_and_si128(data[2], mask0);
308 key[3].xmm = _mm_and_si128(data[3], mask0);
310 const void *key_array[4] = {&key[0], &key[1], &key[2],&key[3]};
312 rte_hash_lookup_bulk(qconf->ipv4_lookup_struct, &key_array[0], 4, ret);
314 dst_port[0] = (ret[0] < 0)? portid:ipv4_l3fwd_out_if[ret[0]];
315 dst_port[1] = (ret[1] < 0)? portid:ipv4_l3fwd_out_if[ret[1]];
316 dst_port[2] = (ret[2] < 0)? portid:ipv4_l3fwd_out_if[ret[2]];
317 dst_port[3] = (ret[3] < 0)? portid:ipv4_l3fwd_out_if[ret[3]];
322 The simple_ipv6_fwd_4pkts() function is similar to the simple_ipv4_fwd_4pkts() function.
324 Known issue: IP packets with extensions or IP packets which are not TCP/UDP cannot work well at this mode.
326 Packet Forwarding for LPM-based Lookups
327 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
329 For each input packet, the packet forwarding operation is done by the l3fwd_simple_forward() function,
330 but the packet forwarding decision (that is, the identification of the output interface for the packet)
331 for LPM-based lookups is done by the get_ipv4_dst_port() function below:
335 static inline uint16_t
336 get_ipv4_dst_port(struct ipv4_hdr *ipv4_hdr, uint16_t portid, lookup_struct_t *ipv4_l3fwd_lookup_struct)
340 return ((rte_lpm_lookup(ipv4_l3fwd_lookup_struct, rte_be_to_cpu_32(ipv4_hdr->dst_addr), &next_hop) == 0)? next_hop : portid);