API: Setting the Priority of a Flow

The priority of a flow can be set in a flow rule as shown in the following example.

/* Create group 1 exact match 5-tuple to retransmit offloaded IPv4 UDP packets. */
struct rte_flow_attr attr = { .group = 1, .priority = 2, .ingress = 1 };

struct rte_flow_item_ipv4 ipv4 = { .hdr = {
  .src_addr = RTE_BE32(0x12345678),
  .dst_addr = RTE_BE32(0xbaddecaf) }};
struct rte_flow_item_udp udp = { .hdr = {
  .src_port = RTE_BE16(0x1000),
  .dst_port = RTE_BE16(0x1001) }};
struct rte_flow_item pattern[] = {
  [0] = { .type = RTE_FLOW_ITEM_TYPE_IPV4, .spec = &ipv4, .mask = &rte_flow_item_ipv4_mask },
  [1] = { .type = RTE_FLOW_ITEM_TYPE_UDP, .spec = &udp, .mask = &rte_flow_item_udp_mask }};

struct rte_flow_action_port_id port_id = { .id = 1 };
struct rte_flow_action action[] = {
  [0] = { .type = RTE_FLOW_ACTION_TYPE_PORT_ID, .conf = &port_id }};

struct rte_flow_error error;
struct rte_flow *flow = rte_flow_create(PORT_ID, &attr, pattern, action, &error);
if (!flow) {
  /* Error handling */
}

The priority attribute in the rte_flow_attr structure specifies the relative priority of the flow compared to other flows. A value in the range of 0 to 3 can be set, where 0 indicates the highest priority. Setting the priority attribute ensures that flows with lower priority are discarded first in cases of network congestion or oversubscription on the TX port.