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// typedef: introduces alternate type name
typedef bit<48> macAddr_t;
typedef bit<32> ip4Addr_t;
// headers: ordered collection of members
// operations test and set validity bits:
// isValid(), setValid(), setInvalid()
header ethernet_t {
macAddr_t dstAddr;
macAddr_t srcAddr;
bit<16> type;
}
// variable declaration and member access
ethernet_t ethernet;
macAddr_t src = ethernet.srcAddr;
// struct: unordered collection of members
struct headers_t {
ethernet_t ethernet;
}
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// packet_in: extern for input packet
extern packet_in {
void extract<T>(out T hdr);
void extract<T>(out T hdr,in bit<32> n);
T lookahead<T>();
void advance(in bit<32> n);
bit<32> length();
}
// parser: begins in special "start" state
state start {
transition parse_ethernet;
}
// User-defined parser state
state parse_ethernet {
packet.extract(hdr.ethernet);
transition select(hdr.ethernet.type) {
0x800: parse_ipv4;
default: accept;
}
}
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// Local metadata declaration, assignment
bit<16> tmp1; bit<16> tmp2;
tmp1 = hdr.ethernet.type;
// bit slicing, concatenation
tmp2 = tmp1[7:0] ++ tmp1[15:8];
// addition, subtraction, casts
tmp2 = tmp1 + tmp1 - (bit<16>)tmp1[7:0];
// bitwise operators
tmp2 = (~tmp1 & tmp1) | (tmp1 ^ tmp1);
tmp2 = tmp1 << 3;
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// Inputs provided by control-plane
action set_next_hop(bit<32> next_hop) {
if (next_hop == 0) {
metadata.next_hop = hdr.ipv4.dst;
}else {
metadata.next_hop = next_hop;
}
}
// Inputs provided by data-plane
action swap_mac(inout bit<48> x,
inout bit<48> y) {
bit<48> tmp = x;
x = y;
y = tmp;
}
// Inputs provided by control/data-plane
action forward(in bit<9> p, bit<48> d) {
standard_metadata.egress_spec = p;
headers.ethernet.dstAddr = d;
}
// Remove header from packet
action decap_ip_ip() {
hdr.ipv4 = hdr.inner_ipv4;
hdr.inner_ipv4.setInvalid();
}
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table ipv4_lpm {
key = {
hdr.ipv4.dstAddr : lpm;
// standard match kinds:
// exact, ternary, lpm
}
// actions that can be invoked
actions = {
ipv4_forward;
drop;
NoAction;
}
// table properties
size = 1024;
default_action = NoAction();
}
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apply {
// branch on header validity
if (hdr.ipv4.isValid()) {
ipv4_lpm.apply();
}
// branch on table hit result
if (local_ip_table.apply().hit) {
send_to_cpu();
}
// branch on table action invocation
switch (table1.apply().action_run) {
action1: { table2.apply(); }
action2: { table3.apply(); }
}
}
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// packet_out: extern for output packet
extern packet_out {
void emit<T>(in T hdr);
}
apply {
// insert headers into pkt if valid
packet.emit(hdr.ethernet);
}
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