mirror of
https://code.semirocket.science/wrapsix
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Generalised translation of ICMPv4 error packets
This commit is contained in:
Michal Zima
parent
d1a25aee7f
commit
c9c167871c
427
src/icmp.c
427
src/icmp.c
@ -32,6 +32,11 @@
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#include "udp.h"
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#include "wrapper.h"
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/* declarations */
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int sub_icmp4_error(unsigned char *payload, unsigned short payload_size,
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unsigned char *packet, unsigned short *packet_len,
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struct s_icmp **icmp, struct s_nat **connection);
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/**
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* Processing of incoming ICMPv4 packets. Directly sends translated ICMPv6
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* packets.
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@ -61,14 +66,10 @@ int icmp_ipv4(struct s_ethernet *eth4, struct s_ipv4 *ip4,
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struct s_ipv6 *ip6;
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/* for error messages */
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unsigned short payload_size_left, new_len;
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struct s_ipv4 *eip4;
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struct s_ipv6 *eip6;
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struct s_tcp *etcp;
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struct s_udp *eudp;
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struct s_icmp *eicmp;
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unsigned short eip4_hlen;
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struct s_ipv6_fragment *eip6_frag;
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unsigned short new_len = sizeof(struct s_ethernet) +
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sizeof(struct s_ipv6);
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/* sanity check */
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if (payload_size < sizeof(struct s_icmp) + 4) {
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@ -112,208 +113,34 @@ int icmp_ipv4(struct s_ethernet *eth4, struct s_ipv4 *ip4,
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/* override information in original ICMP header */
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icmp->type = ICMPV6_ECHO_REPLY;
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new_len = sizeof(struct s_ethernet) +
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sizeof(struct s_ipv6);
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/* copy the payload data */
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payload_size_left = payload_size >
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MTU - sizeof(struct s_ipv6) ?
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MTU - sizeof(struct s_ipv6) : payload_size;
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memcpy(&packet[new_len], payload, payload_size_left);
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icmp = (struct s_icmp *) &packet[new_len];
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new_len += payload_size_left;
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if (payload_size < MTU - sizeof(struct s_ipv6)) {
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memcpy(&packet[new_len], payload, payload_size);
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icmp = (struct s_icmp *) &packet[new_len];
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new_len += payload_size;
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} else {
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memcpy(&packet[new_len], payload, MTU -
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sizeof(struct s_ipv6));
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icmp = (struct s_icmp *) &packet[new_len];
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new_len += MTU - sizeof(struct s_ipv6);
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}
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break;
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case ICMPV4_DST_UNREACHABLE:
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if (icmp->code <= 13 || icmp->code == 15) {
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/* sanity check */
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payload_size_left = payload_size -
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sizeof(struct s_icmp) - 4;
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if (payload_size_left < 1) {
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log_debug("Too short ICMPv4 packet 2");
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if (sub_icmp4_error(icmp_data + 4,
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payload_size - sizeof(struct s_icmp) - 4,
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&packet[0], &new_len, &icmp, &connection)) {
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/* something went wrong */
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return 1;
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}
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/* skip unused space */
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icmp_data += 4;
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/* parse IPv4 header */
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eip4 = (struct s_ipv4 *) icmp_data;
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/* # of 4 byte words */
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eip4_hlen = (eip4->ver_hdrlen & 0x0f) * 4;
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/* sanity check */
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if (payload_size_left < eip4_hlen + 4) {
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log_debug("Too short ICMPv4 packet 3");
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return 1;
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}
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/* 4 B -> L4 addrs */
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payload_size_left -= eip4_hlen + 4;
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icmp_data += eip4_hlen;
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new_len = sizeof(struct s_ethernet) +
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sizeof(struct s_ipv6);
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/* define new inner IPv6 header */
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/* new_len+4+4+40=102 < 1280 */
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eip6 = (struct s_ipv6 *) &packet[new_len +
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eip4 = (struct s_ipv4 *) (icmp_data + 4);
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eip6 = (struct s_ipv6 *) &packet[
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sizeof(struct s_ethernet) +
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sizeof(struct s_ipv6) +
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sizeof(struct s_icmp) + 4];
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/* we'll need this right now */
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ipv4_to_ipv6(&eip4->ip_dest, &eip6->ip_dest);
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/* look for the original connection */
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switch (eip4->proto) {
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case IPPROTO_TCP:
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etcp = (struct s_tcp *)
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icmp_data;
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connection = nat_in(nat4_tcp,
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eip4->ip_dest,
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etcp->port_dest,
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etcp->port_src);
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if (connection == NULL) {
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log_debug("Incoming "
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"TCP error "
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"connection "
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"wasn't found "
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"in NAT");
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return 1;
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}
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/* fix port for local client */
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etcp->port_src = connection->
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ipv6_port_src;
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break;
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case IPPROTO_UDP:
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eudp = (struct s_udp *)
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icmp_data;
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connection = nat_in(nat4_udp,
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eip4->ip_dest,
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eudp->port_dest,
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eudp->port_src);
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if (connection == NULL) {
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log_debug("Incoming "
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"UDP error "
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"connection "
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"wasn't found "
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"in NAT");
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return 1;
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}
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/* fix port for local client */
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eudp->port_src = connection->
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ipv6_port_src;
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break;
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case IPPROTO_ICMP:
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eicmp = (struct s_icmp *)
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icmp_data;
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/* we translate only echo
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* requests so handle only them
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* here too */
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if (eicmp->type !=
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ICMPV4_ECHO_REQUEST) {
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log_debug("Unknown ICMP"
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" type within "
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"ICMP error");
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return 1;
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}
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/* else: */
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/* sanity check */
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if (payload_size_left < 4) {
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log_debug("Too short "
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"ICMPv4 packet "
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"4");
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return 1;
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}
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echo = (struct s_icmp_echo *)
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(icmp_data +
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sizeof(struct s_icmp));
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connection = nat_in(nat4_icmp,
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eip4->ip_dest, 0,
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echo->id);
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if (connection == NULL) {
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log_debug("Incoming "
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"ICMP error "
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"connection "
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"wasn't found "
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"in NAT");
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return 1;
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}
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/* fix port for local client */
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echo->id = connection->
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ipv6_port_src;
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/* adjust ICMP type */
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eicmp->type =
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ICMPV6_ECHO_REQUEST;
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break;
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default:
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/* we don't know where to send
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* it */
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return 1;
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}
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/* copy ICMP header to new packet */
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memcpy(&packet[new_len], icmp,
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sizeof(struct s_icmp) + 4);
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icmp = (struct s_icmp *) &packet[new_len];
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new_len += sizeof(struct s_icmp) + 4;
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/* complete inner IPv6 header */
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eip6->ver = 0x60 | (eip4->tos >> 4);
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eip6->traffic_class = eip4->tos << 4;
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eip6->flow_label = 0x0;
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eip6->hop_limit = eip4->ttl;
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if (eip4->proto != IPPROTO_ICMP) {
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eip6->next_header = eip4->proto;
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} else {
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eip6->next_header = IPPROTO_ICMPV6;
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}
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eip6->ip_src = connection->ipv6;
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new_len += sizeof(struct s_ipv6);
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/* was the IPv4 packet fragmented? */
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if ((eip4->flags_offset & htons(0x1fff)) !=
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0x0000) {
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/* original length of error packet,
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* but without IP header, but with
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* fragment header(!) */
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eip6->len = htons(ntohs(eip4->len) -
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eip4_hlen +
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sizeof(struct s_ipv6_fragment));
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eip6_frag = (struct s_ipv6_fragment *)
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&packet[new_len];
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eip6_frag->next_header =
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eip6->next_header;
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eip6->next_header = IPPROTO_FRAGMENT;
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eip6_frag->id = htonl(ntohs(eip4->id));
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new_len +=
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sizeof(struct s_ipv6_fragment);
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} else {
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eip6->len = htons(ntohs(eip4->len) -
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eip4_hlen);
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}
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/* translate ICMP type&code */
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if (icmp->code == 2) {
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@ -382,24 +209,6 @@ int icmp_ipv4(struct s_ethernet *eth4, struct s_ipv4 *ip4,
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icmp->code = 0;
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}
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/* copy payload, aligned to MTU */
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/* we can afford to use full MTU instead of
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* just 1280 B as admin warrants this to us */
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if (payload_size - sizeof(struct s_icmp) - 4 -
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eip4_hlen > (unsigned int) MTU - new_len) {
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memcpy(&packet[new_len], icmp_data,
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MTU - new_len);
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new_len = MTU;
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} else {
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memcpy(&packet[new_len], icmp_data,
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payload_size -
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sizeof(struct s_icmp) - 4 -
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eip4_hlen);
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new_len += payload_size -
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sizeof(struct s_icmp) - 4 -
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eip4_hlen;
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}
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/* new packet is almost finished, yay! */
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break;
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@ -425,7 +234,8 @@ int icmp_ipv4(struct s_ethernet *eth4, struct s_ipv4 *ip4,
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ip6->ver = 0x60 | (ip4->tos >> 4);
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ip6->traffic_class = ip4->tos << 4;
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ip6->flow_label = 0x0;
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ip6->len = htons(new_len - sizeof(struct s_ethernet) - sizeof(struct s_ipv6));
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ip6->len = htons(new_len - sizeof(struct s_ethernet) -
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sizeof(struct s_ipv6));
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ip6->next_header = IPPROTO_ICMPV6;
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ip6->hop_limit = ip4->ttl;
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ipv4_to_ipv6(&ip4->ip_src, &ip6->ip_src);
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@ -818,3 +628,186 @@ int icmp6_error(struct s_mac_addr mac_dest, struct s_ipv6_addr ip_dest,
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return 0;
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}
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/**
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* Helper function for translating inner packet in ICMPv4 error.
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*
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* @param payload Original inner packet data
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* @param payload_size Length of original data
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* @param packet Space for translated packet data
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* @param packet_len Length of translated data
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* @param icmp Outer ICMP header
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* @param connection NAT connection for inner packet
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*
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* @return 0 for success
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* @return 1 for failure
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*/
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int sub_icmp4_error(unsigned char *payload, unsigned short payload_size,
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unsigned char *packet, unsigned short *packet_len,
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struct s_icmp **icmp, struct s_nat **connection)
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{
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struct s_ipv4 *eip4;
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struct s_ipv6 *eip6;
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struct s_tcp *etcp;
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struct s_udp *eudp;
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struct s_icmp *eicmp;
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unsigned short eip4_hlen;
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struct s_ipv6_fragment *eip6_frag;
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struct s_icmp_echo *echo;
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/* sanity check */
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if (payload_size < 1) {
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log_debug("Too short ICMPv4 packet 2");
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return 1;
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}
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/* parse IPv4 header */
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eip4 = (struct s_ipv4 *) payload;
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/* # of 4 byte words */
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eip4_hlen = (eip4->ver_hdrlen & 0x0f) * 4;
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/* sanity check */
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if (payload_size < eip4_hlen + 4) {
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log_debug("Too short ICMPv4 packet 3");
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return 1;
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}
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/* 4 B -> L4 addrs */
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payload_size -= eip4_hlen;
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payload += eip4_hlen;
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/* define new inner IPv6 header */
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/* new_len+4+4+40=102 < 1280 */
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eip6 = (struct s_ipv6 *) &packet[*packet_len + sizeof(struct s_icmp) +
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4];
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/* we'll need this right now */
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ipv4_to_ipv6(&eip4->ip_dest, &eip6->ip_dest);
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/* look for the original connection */
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switch (eip4->proto) {
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case IPPROTO_TCP:
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etcp = (struct s_tcp *) payload;
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*connection = nat_in(nat4_tcp, eip4->ip_dest,
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etcp->port_dest, etcp->port_src);
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if (*connection == NULL) {
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log_debug("Incoming TCP error connection "
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"wasn't found in NAT");
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return 1;
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}
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/* fix port for local client */
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etcp->port_src = (*connection)->ipv6_port_src;
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break;
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case IPPROTO_UDP:
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eudp = (struct s_udp *) payload;
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*connection = nat_in(nat4_udp, eip4->ip_dest,
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eudp->port_dest, eudp->port_src);
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if (*connection == NULL) {
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log_debug("Incoming UDP error connection "
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"wasn't found in NAT");
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return 1;
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}
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/* fix port for local client */
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eudp->port_src = (*connection)->ipv6_port_src;
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break;
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case IPPROTO_ICMP:
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eicmp = (struct s_icmp *) payload;
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/* we translate only echo requests so handle only them
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* here too */
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if (eicmp->type != ICMPV4_ECHO_REQUEST) {
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log_debug("Unknown ICMP type within ICMP "
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"error");
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return 1;
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}
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/* else: */
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/* sanity check */
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if (payload_size < 8) {
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log_debug("Too short ICMPv4 packet 4");
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return 1;
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}
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echo = (struct s_icmp_echo *) (payload +
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sizeof(struct s_icmp));
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*connection = nat_in(nat4_icmp, eip4->ip_dest, 0,
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echo->id);
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if (*connection == NULL) {
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log_debug("Incoming ICMP error connection "
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"wasn't found in NAT");
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return 1;
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}
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/* fix port for local client */
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echo->id = (*connection)->ipv6_port_src;
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/* adjust ICMP type */
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eicmp->type = ICMPV6_ECHO_REQUEST;
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break;
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default:
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/* we don't know where to send it */
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return 1;
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}
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/* copy ICMP header to new packet */
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memcpy(&packet[*packet_len], *icmp, sizeof(struct s_icmp) + 4);
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*icmp = (struct s_icmp *) &packet[*packet_len];
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/* complete inner IPv6 header */
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eip6->ver = 0x60 | (eip4->tos >> 4);
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eip6->traffic_class = eip4->tos << 4;
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eip6->flow_label = 0x0;
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eip6->hop_limit = eip4->ttl;
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if (eip4->proto != IPPROTO_ICMP) {
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eip6->next_header = eip4->proto;
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} else {
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eip6->next_header = IPPROTO_ICMPV6;
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}
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eip6->ip_src = (*connection)->ipv6;
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*packet_len += sizeof(struct s_icmp) + 4 + sizeof(struct s_ipv6);
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/* was the IPv4 packet fragmented? */
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if ((eip4->flags_offset & htons(0x1fff)) != 0x0000) {
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/* original length of error packet,
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* but without IP header, but with
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* fragment header(!) */
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eip6->len = htons(ntohs(eip4->len) - eip4_hlen +
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sizeof(struct s_ipv6_fragment));
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eip6_frag = (struct s_ipv6_fragment *) &packet[*packet_len];
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eip6_frag->next_header = eip6->next_header;
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eip6->next_header = IPPROTO_FRAGMENT;
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eip6_frag->id = htonl(ntohs(eip4->id));
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*packet_len += sizeof(struct s_ipv6_fragment);
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} else {
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eip6->len = htons(ntohs(eip4->len) - eip4_hlen);
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}
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/* copy payload, aligned to MTU */
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/* we can afford to use full MTU instead of just 1280 B as admin
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* warrants this to us */
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if (payload_size > (unsigned int) MTU - *packet_len) {
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memcpy(&packet[*packet_len], payload, MTU - *packet_len);
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*packet_len = MTU;
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} else {
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memcpy(&packet[*packet_len], payload, payload_size);
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*packet_len += payload_size;
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}
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return 0;
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}
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