#define EGRESS_IPV6_ACL_KEY \
EGRESS_ACL_KEY_PORT_LABEL : ternary; \
EGRESS_ACL_KEY_BD_LABEL : ternary; \
EGRESS_ACL_KEY_IPV6_SA : ternary; \
EGRESS_ACL_KEY_IPV6_DA : ternary; \
EGRESS_ACL_KEY_IPV6_PROTO : ternary;
Using define to declare new set of variable - ternary?
#if defined(INT_ENABLE) || defined(POSTCARD_ENABLE)
@pragma pa_do_not_bridge egress i2e_metadata.mirror_session_id
#endif
Checking if INT_ENABLE or POSTCARD_ENABLE flags are defined, and if so, adds a pragma code
/*****************************************************************************/
/* Egress ACL l4 port range */
/*****************************************************************************/
...
control process_egress_l4port {
#ifdef EGRESS_ACL_ENABLE
apply(egress_l4port_fields);
#ifndef EGRESS_ACL_RANGE_DISABLE
apply(egress_l4_src_port);
apply(egress_l4_dst_port);
#endif /* EGRESS_ACL_RANGE_DISABLE */
#endif /* EGRESS_ACL_ENABLE */
}
Using ifdef and ifndef to check if specific flags are set or not and depending on that, inserts apply respective apply statements in the control block
header_type egress_metadata_t {
fields {
#ifdef PTP_ENABLE
capture_tstamp_on_tx : 1; /* request for packet departure time capture */
#endif
bypass : 1; /* bypass egress pipeline */
port_type : 2; /* egress port type */
payload_length : 16; /* payload length for tunnels */
...
}
}
Using ifdef to insert new fields in the egress_metadata_t header struct
#ifdef SFLOW_ENABLE
@pragma pa_atomic ingress ingress_metadata.sflow_take_sample
@pragma pa_solitary ingress ingress_metadata.sflow_take_sample
#endif
Using ifdef to insert pragma statements
control ingress {
/* input mapping - derive an ifindex */
process_ingress_port_mapping();
/* read and apply system configuration parametes */
process_global_params();
#ifdef PKTGEN_ENABLE
if (VALID_PKTGEN_PACKET) {
/* process pkt_gen generated packets */
process_pktgen();
} else {
#endif /* PKTGEN_ENABLE */
/* process outer packet headers */
process_validate_outer_header();
...
}
...
}
Using ifdef to insert control block statements, which potentially change the scope of some lines in this case because an if and else conditions are added if the flag is defined
if (l2_metadata.lkp_pkt_type == L2_UNICAST) {
#if defined(L2_DISABLE) && defined(L2_MULTICAST_DISABLE) && defined(L3_MULTICAST_DISABLE)
{
{
#else
apply(rmac) {
rmac_hit {
#endif /* L2_DISABLE && L2_MULTICAST_DISABLE && L3_MULTICAST_DISABLE */
if (DO_LOOKUP(L3)) {
if ((l3_metadata.lkp_ip_type == IPTYPE_IPV4) and
(ipv4_metadata.ipv4_unicast_enabled == TRUE)) {
/* router ACL/PBR */
#ifndef RACL_SWAP
process_ipv4_racl();
#endif /* !RACL_SWAP */
process_ipv4_urpf();
process_ipv4_fib();
#ifdef RACL_SWAP
process_ipv4_racl();
#endif /* RACL_SWAP */
#ifdef IPV6_DISABLE
}
#else
} else {
if ((l3_metadata.lkp_ip_type == IPTYPE_IPV6) and
(ipv6_metadata.ipv6_unicast_enabled == TRUE)) {
/* router ACL/PBR */
#ifndef RACL_SWAP
process_ipv6_racl();
#endif /* !RACL_SWAP */
process_ipv6_urpf();
process_ipv6_fib();
#ifdef RACL_SWAP
process_ipv6_racl();
#endif /* RACL_SWAP */
}
}
#endif /* IPV6_DISABLE */
process_urpf_bd();
}
}
}
} else {
process_multicast();
}
A big block of code whose scope is defined by the flags. if, else, and else if statements are added to the change how this block works when compiled. For instance, in the starting of this block, we either define this as a function or as a apply block based on the L2_DISABLE, L2_MULTICAST_DISABLE, L3_MULTICAST_DISABLE flags
...
/* Standard Model */
#define EGRESS_FILTER
#define FABRIC_ENABLE
#define EGRESS_ACL_ENABLE
...
All required flags being defined in a header file using define
header_type fabric_metadata_t {
fields {
packetType : 3;
fabric_header_present : 1;
reason_code : 16; /* cpu reason code */
#ifdef FABRIC_ENABLE
dst_device : 8; /* destination device id */
dst_port : 16; /* destination port id */
#endif /* FABRIC_ENABLE */
}
}
Using ifdef to add new header fields depending on whether fabric mode is enabled or not
#ifdef FABRIC_ENABLE
action terminate_fabric_unicast_packet() {
...
}
action switch_fabric_unicast_packet() {
...
}
#ifndef MULTICAST_DISABLE
action terminate_fabric_multicast_packet() {
...
}
action switch_fabric_multicast_packet() {
...
}
#endif /* MULTICAST_DISABLE */
#endif /* FABRIC_ENABLE */
/*****************************************************************************/
/* Fabric header - source lookup */
/*****************************************************************************/
#ifdef FABRIC_ENABLE
action set_ingress_ifindex_properties(l2xid) {
modify_field(ig_intr_md_for_tm.level2_exclusion_id, l2xid);
}
table fabric_ingress_src_lkp {
reads {
fabric_header_multicast.ingressIfindex : exact;
}
actions {
nop;
set_ingress_ifindex_properties;
}
size : 1024;
}
#endif /* FABRIC_ENABLE */
Again checking if fabric mode is enabled and inserting new actions and tables related ot fabric mode depending on the flag
/*****************************************************************************/
/* Ingress fabric header processing */
/*****************************************************************************/
control process_ingress_fabric {
if (ingress_metadata.port_type != PORT_TYPE_NORMAL) {
apply(fabric_ingress_dst_lkp);
#ifdef FABRIC_ENABLE
if (ingress_metadata.port_type == PORT_TYPE_FABRIC) {
if (valid(fabric_header_multicast)) {
apply(fabric_ingress_src_lkp);
}
if (tunnel_metadata.tunnel_terminate == FALSE) {
apply(native_packet_over_fabric);
}
}
#endif /* FABRIC_ENABLE */
}
}
Another place where statements are inserted in a control block based on the FABRIC_ENABLED flag. Many more similar instances occur in this file that depend on whether the FABRIC_ENABLED flag is defined or not
Source:
header_type multicast_metadata_t {
fields {
...
#ifdef FABRIC_ENABLE
mcast_grp_a : 16;
mcast_grp_b : 16;
ingress_rid : 16;
l1_exclusion_id : 16;
#endif /* FABRIC_ENABLE */
}
}
Again checking for the FABRIC_ENABLE flag using ifdef and depending on that we have extra header fields
table validate_outer_ipv4_packet {
reads {
...
#if !defined(L2_MULTICAST_DISABLE) || !defined(L3_MULTICAST_DISABLE)
ipv4.dstAddr mask 0xFFFFFF00 : ternary;
#endif /* !defined(L2_MULTICAST_DISABLE) || !defined(L3_MULTICAST_DISABLE) */
}
actions {
set_valid_outer_ipv4_packet;
#if !defined(L2_MULTICAST_DISABLE) || !defined(L3_MULTICAST_DISABLE)
set_valid_outer_ipv4_llmc_packet;
set_valid_outer_ipv4_mc_packet;
#endif /* !defined(L2_MULTICAST_DISABLE) || !defined(L3_MULTICAST_DISABLE) */
set_malformed_outer_ipv4_packet;
}
size : VALIDATE_PACKET_TABLE_SIZE;
}
#endif /* L3_DISABLE && IPV4_DISABLE */
Using if and defined to check if L2_MULTICAST_DISABLE and other flags are defined or not to insert statements into the table readers and actions
control process_ipv4_urpf {
#if !defined(L3_DISABLE) && !defined(IPV4_DISABLE) && !defined(URPF_DISABLE)
/* unicast rpf lookup */
if (ipv4_metadata.ipv4_urpf_mode != URPF_MODE_NONE) {
#ifdef IPV4_LOCAL_HOST_TABLE_SIZE
apply(ipv4_local_hosts_urpf) {
on_miss {
#endif
apply(ipv4_urpf) {
on_miss {
apply(ipv4_urpf_lpm);
}
}
#ifdef IPV4_LOCAL_HOST_TABLE_SIZE
}
}
#endif
}
#endif /* L3_DISABLE && IPV4_DISABLE && URPF_DISABLE */
}
In this case, they have a control block fille with statement iff either of those three flags are not defined, and an outer apply statement is added iff the IPV4_LOCAL_HOST_TABLE_SIZE is defined. So control block and apply blocks are added based on certain flags, which are checked using if, ifdef, and defined