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#include "proto.h"
#include "util.h"
#include <string.h>
enum {
Type = 0,
Code = 1,
Checksum = 2,
Payload = 4,
};
void icmp_parse(const uint8_t *buf, size_t len, struct ipv4 ip) {
if (len < Payload) return;
uint8_t type = buf[Type];
if (type == 8 && ip.dst == state.ip) {
/* echo reply */
uint8_t *pkt = icmp_start(len - Payload, (struct icmp){
.type = 0,
.ip.dst = ip.src,
.ip.e.dst = ip.e.src,
});
memcpy(pkt, buf + Payload, len - Payload);
icmp_finish(pkt);
}
}
uint8_t *icmp_start(size_t len, struct icmp i) {
i.ip.proto = 1;
uint8_t *pkt = ipv4_start(Payload + len, i.ip);
pkt[Type] = i.type;
pkt[Code] = i.code;
nput16(pkt + Checksum, ip_checksum(pkt, Payload + len));
return pkt + Payload;
}
void icmp_finish(uint8_t *pkt) {
ipv4_finish(pkt - Payload);
}
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