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fix checksum

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mykola2312 2024-12-19 19:01:26 +02:00
parent 075a8bd3bc
commit a75a35810a
1 changed files with 9 additions and 5 deletions
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14
main.c
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@ -179,7 +179,7 @@ uint16_t checksum(const uint8_t* data, size_t len) {
uint32_t sum = 0; uint32_t sum = 0;
for (size_t i = 0; i < len / 2; i++) { for (size_t i = 0; i < len / 2; i++) {
sum += *((const uint16_t*)data + i); sum += *((const uint16_t*)data + i);
sum += sum >> 16; sum = (sum >> 16) + (sum & 0xFFFF);
} }
return ~((uint16_t)sum); return ~((uint16_t)sum);
@ -227,21 +227,25 @@ int main(int argc, char** argv) {
uint16_t id = (uint16_t)rand(); uint16_t id = (uint16_t)rand();
// ICMP request // ICMP request
struct icmphdr* icmp = frame_new(sizeof(struct icmphdr)); size_t hdrlen = sizeof(struct icmphdr);
size_t payloadlen = 32;
struct icmphdr* icmp = frame_new(hdrlen + payloadlen);
icmp->type = ICMP_ECHO; icmp->type = ICMP_ECHO;
icmp->code = 0; icmp->code = 0;
icmp->checksum = 0; icmp->checksum = 0;
icmp->un.echo.id = (uint16_t)rand(); icmp->un.echo.id = (uint16_t)rand();
icmp->un.echo.sequence = 1; icmp->un.echo.sequence = 1;
// set payload
memset(icmp + 1, 69, payloadlen);
// calculate checksum // calculate checksum
icmp->checksum = htons(checksum( icmp->checksum = checksum((const uint8_t*)icmp, hdrlen + payloadlen);
(const uint8_t*)&icmp, sizeof(struct icmphdr)));
// IPv4 local broadcast // IPv4 local broadcast
uint8_t ip_broadcast[4] = {255, 255, 255, 255}; uint8_t ip_broadcast[4] = {255, 255, 255, 255};
ssize_t sent = ip_send(link, target, ip_broadcast, ssize_t sent = ip_send(link, target, ip_broadcast,
IPPROTO_ICMP, icmp, sizeof(struct icmphdr)); IPPROTO_ICMP, icmp, hdrlen + payloadlen);
printf("sent %ld\n", sent); printf("sent %ld\n", sent);
link_free(link); link_free(link);