void icmp_in(struct pkbuf *pkb)
{
struct ip *iphdr = pkb2ip(pkb);
struct icmp *icmphdr = ip2icmp(iphdr);
int icmplen, type;
/* sanity check */
icmplen = ipdlen(iphdr);
icmpdbg("%d bytes", icmplen);
if (icmplen < ICMP_HRD_SZ) {
icmpdbg("icmp header is too small");
goto drop_pkb;
}
if (icmp_chksum((unsigned short *)icmphdr, icmplen) != 0) {
icmpdbg("icmp checksum is error");
goto drop_pkb;
}
type = icmphdr->icmp_type;
if (type > ICMP_T_MAXNUM) {
icmpdbg("unknown icmp type %d code %d",
type, icmphdr->icmp_code);
goto drop_pkb;
}
/* handle icmp type */
icmp_table[type].handler(&icmp_table[type], pkb);
return;
drop_pkb:
free_pkb(pkb);
}
static void icmp_echo_request(struct icmp_desc *icmp_desc, struct pkbuf *pkb)
{
struct ip *iphdr = pkb2ip(pkb);
struct icmp *icmphdr = ip2icmp(iphdr);
icmpdbg("echo request data %d bytes icmp_id %d icmp_seq %d",
(int)(iphdr->ip_len - iphlen(iphdr) - ICMP_HRD_SZ),
_ntohs(icmphdr->icmp_id),
_ntohs(icmphdr->icmp_seq));
if (icmphdr->icmp_code) {
icmpdbg("echo request packet corrupted");
free_pkb(pkb);
return;
}
icmphdr->icmp_type = ICMP_T_ECHORLY;
/*
* adjacent the checksum:
* If ~ >>> (cksum + x + 8) >>> == 0
* let ~ >>> (cksum` + x ) >>> == 0
* then cksum` = cksum + 8
*/
if (icmphdr->icmp_cksum >= 0xffff - ICMP_T_ECHOREQ)
icmphdr->icmp_cksum += ICMP_T_ECHOREQ + 1;
else
icmphdr->icmp_cksum += ICMP_T_ECHOREQ;
iphdr->ip_dst = iphdr->ip_src; /* ip_src is set by ip_send_out() */
ip_hton(iphdr);
/* init reused input packet */
pkb->pk_rtdst = NULL;
pkb->pk_indev = NULL;
pkb->pk_type = PKT_NONE;
ip_send_out(pkb);
}
static void icmp_drop_reply(struct icmp_desc *icmp_desc, struct pkbuf *pkb)
{
struct ip *iphdr = pkb2ip(pkb);
struct icmp *icmphdr = ip2icmp(iphdr);
icmpdbg("icmp type %d code %d (dropped)",
icmphdr->icmp_type, icmphdr->icmp_code);
if (icmp_desc->info)
icmpdbg("%s", icmp_desc->info);
free_pkb(pkb);
}
static void icmp_echo_reply(struct icmp_desc *icmp_desc, struct pkbuf *pkb)
{
struct ip *iphdr = pkb2ip(pkb);
struct icmp *icmphdr = ip2icmp(iphdr);
icmpdbg("from "IPFMT" id %d seq %d ttl %d",
ipfmt(iphdr->ip_src),
_ntohs(icmphdr->icmp_id),
_ntohs(icmphdr->icmp_seq),
iphdr->ip_ttl);
free_pkb(pkb);
}
/* NOTE: icmp dont drop @ipkb */
void icmp_send(unsigned char type, unsigned char code,
unsigned int data, struct pkbuf *pkb_in)
{
struct pkbuf *pkb;
struct ip *iphdr = pkb2ip(pkb_in);
struct icmp *icmphdr;
int paylen = _ntohs(iphdr->ip_len); /* icmp payload length */
if (paylen < iphlen(iphdr) + 8)
return;
/*
* RFC 1812 Section 4.3.2.7 for sanity check
* An ICMP error message MUST NOT be sent as the result of receiving:
* 1. A packet sent as a Link Layer broadcast or multicast
* 2. A packet destined to an IP broadcast or IP multicast address
*[3] A packet whose source address has a network prefix of zero or is an
* invalid source address (as defined in Section [5.3.7])
* 4. Any fragment of a datagram other then the first fragment (i.e., a
* packet for which the fragment offset in the IP header is nonzero).
* 5. An ICMP error message
*/
if (pkb_in->pk_type != PKT_LOCALHOST)
return;
if (MULTICAST(iphdr->ip_dst) || BROADCAST(iphdr->ip_dst))
return;
if (iphdr->ip_fragoff & _htons(IP_FRAG_OFF))
return;
if (icmp_type_error(type) && iphdr->ip_pro == IP_P_ICMP) {
icmphdr = ip2icmp(iphdr);
if (icmphdr->icmp_type > ICMP_T_MAXNUM || icmp_error(icmphdr))
return;
}
/* build icmp packet and send */
/* ip packet size must be smaller than 576 bytes */
if (IP_HRD_SZ + ICMP_HRD_SZ + paylen > 576)
paylen = 576 - IP_HRD_SZ - ICMP_HRD_SZ;
pkb = alloc_pkb(ETH_HRD_SZ + IP_HRD_SZ + ICMP_HRD_SZ + paylen);
icmphdr = (struct icmp *)(pkb2ip(pkb)->ip_data);
icmphdr->icmp_type = type;
icmphdr->icmp_code = code;
icmphdr->icmp_cksum = 0;
icmphdr->icmp_undata = data;
memcpy(icmphdr->icmp_data, (unsigned char *)iphdr, paylen);
icmphdr->icmp_cksum =
icmp_chksum((unsigned short *)icmphdr, ICMP_HRD_SZ + paylen);
icmpdbg("to "IPFMT"(payload %d) [type %d code %d]\n",
ipfmt(iphdr->ip_src), paylen, type, code);
ip_send_info(pkb, 0, IP_HRD_SZ + ICMP_HRD_SZ + paylen,
0, IP_P_ICMP, iphdr->ip_src);
}
static void icmp_redirect(struct icmp_desc *icmp_desc, struct pkbuf *pkb)
{
struct ip *iphdr = pkb2ip(pkb);
struct icmp *icmphdr = ip2icmp(iphdr);
if (icmphdr->icmp_code > 4)
icmpdbg("Redirect code %d is error", icmphdr->icmp_code);
else
icmpdbg("from " IPFMT " %s(new nexthop "IPFMT")",
ipfmt(iphdr->ip_src),
redirectstr[icmphdr->icmp_code],
ipfmt(icmphdr->icmp_gw));
free_pkb(pkb);
}
static void recv_packet(void)
{
struct pkbuf *pkb;
struct ip *iphdr;
struct icmp *icmphdr;
while (!finite || recv > 0) {
pkb = _recv(sock);
if (!pkb)
break;
iphdr = pkb2ip(pkb);
icmphdr = ip2icmp(iphdr);
if (iphdr->ip_pro == IP_P_ICMP &&
_ntohs(icmphdr->icmp_id) == id &&
icmphdr->icmp_type == ICMP_T_ECHORLY) {
recv--;
printf("%d bytes from " IPFMT ": icmp_seq=%d ttl=%d\n",
ipdlen(iphdr), ipfmt(iphdr->ip_src),
_ntohs(icmphdr->icmp_seq), iphdr->ip_ttl);
precv++;
}
free_pkb(pkb);
}
}
