mirror of
https://code.semirocket.science/wrapsix
synced 2024-12-22 12:30:18 +02:00
Fragmenting of too big TCPv4 packets
This commit is contained in:
Michal Zima
parent
32deb4f0ee
commit
b28566bc64
13
src/ipv6.h
13
src/ipv6.h
@ -21,6 +21,8 @@
|
||||
|
||||
#include "ethernet.h" /* s_ethernet */
|
||||
|
||||
#define IPV6_FLAG_MORE_FRAGMENTS 0x0001
|
||||
|
||||
/* IPv6 address structure */
|
||||
struct s_ipv6_addr {
|
||||
unsigned char addr[16];
|
||||
@ -38,6 +40,17 @@ struct s_ipv6 {
|
||||
struct s_ipv6_addr ip_dest; /* 128 b; destination address */
|
||||
} __attribute__ ((__packed__));
|
||||
|
||||
/* IPv6 fragment header structure */
|
||||
struct s_ipv6_fragment {
|
||||
unsigned char next_header; /* 8 b; next header */
|
||||
unsigned char zeros; /* 8 b; reserved */
|
||||
unsigned short offset_flag; /* 13 b; fragment offset in B,
|
||||
2 b; reserved,
|
||||
1 b; flag */
|
||||
unsigned int id; /* 32 b; id of the packet
|
||||
(for fragmentation) */
|
||||
} __attribute__ ((__packed__));
|
||||
|
||||
/* IPv6 pseudoheader structure for checksum */
|
||||
struct s_ipv6_pseudo {
|
||||
struct s_ipv6_addr ip_src; /* 128 b; source address */
|
||||
|
||||
195
src/tcp.c
195
src/tcp.c
@ -52,78 +52,149 @@ int tcp_ipv4(struct s_ethernet *eth4, struct s_ipv4 *ip4, char *payload,
|
||||
unsigned short orig_checksum;
|
||||
unsigned char *packet;
|
||||
|
||||
struct s_ethernet *eth6;
|
||||
struct s_ipv6 *ip6;
|
||||
struct s_ethernet *eth6;
|
||||
struct s_ipv6 *ip6;
|
||||
struct s_ipv6_fragment *frag;
|
||||
|
||||
/* parse TCP header */
|
||||
tcp = (struct s_tcp *) payload;
|
||||
/* full processing of unfragmented packet or the first fragment with
|
||||
* TCP header with checksum field (this is safe)
|
||||
*/
|
||||
if ((ip4->flags_offset & htons(IPV4_FLAG_DONT_FRAGMENT)) ||
|
||||
((ip4->flags_offset & htons(IPV4_FLAG_MORE_FRAGMENTS)) &&
|
||||
(ip4->flags_offset & 0xff1f) == 0x0000 &&
|
||||
payload_size >= sizeof(struct s_tcp) - 2)) {
|
||||
/* parse TCP header */
|
||||
tcp = (struct s_tcp *) payload;
|
||||
|
||||
/* checksum recheck */
|
||||
if (tcp->checksum != 0x0000) {
|
||||
orig_checksum = tcp->checksum;
|
||||
tcp->checksum = 0;
|
||||
tcp->checksum = checksum_ipv4(ip4->ip_src, ip4->ip_dest,
|
||||
payload_size, IPPROTO_TCP,
|
||||
(unsigned char *) tcp);
|
||||
/* checksum recheck -- only if the packet is unfragmented */
|
||||
if ((ip4->flags_offset | htons(IPV4_FLAG_DONT_FRAGMENT)) ==
|
||||
htons(IPV4_FLAG_DONT_FRAGMENT)) {
|
||||
orig_checksum = tcp->checksum;
|
||||
tcp->checksum = 0;
|
||||
tcp->checksum = checksum_ipv4(ip4->ip_src, ip4->ip_dest,
|
||||
payload_size, IPPROTO_TCP,
|
||||
(unsigned char *) tcp);
|
||||
|
||||
if (tcp->checksum != orig_checksum) {
|
||||
/* packet is corrupted and shouldn't be processed */
|
||||
printf("[Debug] Wrong checksum\n");
|
||||
if (tcp->checksum != orig_checksum) {
|
||||
/* packet is corrupted and shouldn't be
|
||||
* processed */
|
||||
printf("[Debug] Wrong checksum\n");
|
||||
return 1;
|
||||
}
|
||||
}
|
||||
|
||||
/* find connection in NAT */
|
||||
connection = nat_in(nat4_tcp, ip4->ip_src,
|
||||
tcp->port_src, tcp->port_dest);
|
||||
|
||||
if (connection == NULL) {
|
||||
printf("[Debug] Incoming connection wasn't found in "
|
||||
"NAT\n");
|
||||
return 1;
|
||||
}
|
||||
}
|
||||
|
||||
/* find connection in NAT */
|
||||
connection = nat_in(nat4_tcp, ip4->ip_src, tcp->port_src, tcp->port_dest);
|
||||
/* allocate enough memory for translated packet */
|
||||
if ((packet = (unsigned char *) malloc(
|
||||
payload_size > MTU - sizeof(struct s_ipv6) ?
|
||||
MTU + sizeof(struct s_ethernet) :
|
||||
sizeof(struct s_ethernet) + sizeof(struct s_ipv6) +
|
||||
payload_size)) == NULL) {
|
||||
fprintf(stderr, "[Error] Lack of free memory\n");
|
||||
return 1;
|
||||
}
|
||||
eth6 = (struct s_ethernet *) packet;
|
||||
ip6 = (struct s_ipv6 *) (packet + sizeof(struct s_ethernet));
|
||||
|
||||
if (connection == NULL) {
|
||||
printf("[Debug] Incoming connection wasn't found in NAT\n");
|
||||
/* build ethernet header */
|
||||
eth6->dest = connection->mac;
|
||||
eth6->src = mac;
|
||||
eth6->type = htons(ETHERTYPE_IPV6);
|
||||
|
||||
/* build IPv6 header */
|
||||
ip6->ver = 0x60 | (ip4->tos >> 4);
|
||||
ip6->traffic_class = ip4->tos << 4;
|
||||
ip6->flow_label = 0x0;
|
||||
ip6->hop_limit = ip4->ttl;
|
||||
ipv4_to_ipv6(&ip4->ip_src, &ip6->ip_src);
|
||||
memcpy(&ip6->ip_dest, &connection->ipv6,
|
||||
sizeof(struct s_ipv6_addr));
|
||||
|
||||
/* set incoming source port */
|
||||
tcp->port_dest = connection->ipv6_port_src;
|
||||
|
||||
/* compute TCP checksum */
|
||||
tcp->checksum = checksum_ipv6_update(tcp->checksum,
|
||||
ip4->ip_src, ip4->ip_dest,
|
||||
connection->ipv4_port_src,
|
||||
ip6->ip_src, ip6->ip_dest,
|
||||
connection->ipv6_port_src);
|
||||
|
||||
/* fragment it or not? */
|
||||
if (payload_size > MTU - sizeof(struct s_ipv6)) {
|
||||
/* 1st fragments' payload size must be 8-byte aligned */
|
||||
#define FRAGMENT_LEN (((MTU - sizeof(struct s_ipv6) - \
|
||||
sizeof(struct s_ipv6_fragment)) / 8) * 8)
|
||||
|
||||
/* fill in missing IPv6 header fields */
|
||||
ip6->len = htons(FRAGMENT_LEN +
|
||||
sizeof(struct s_ipv6_fragment));
|
||||
ip6->next_header = IPPROTO_FRAGMENT;
|
||||
|
||||
/* create IPv6 fragment header */
|
||||
frag = (struct s_ipv6_fragment *) ((unsigned char *) ip6
|
||||
+ sizeof(struct s_ipv6));
|
||||
frag->next_header = IPPROTO_TCP;
|
||||
frag->zeros = 0x0;
|
||||
frag->offset_flag = htons(IPV6_FLAG_MORE_FRAGMENTS);
|
||||
frag->id = ip4->id ? htonl(htons(ip4->id)) :
|
||||
(unsigned int) rand();
|
||||
|
||||
/* copy the payload data */
|
||||
memcpy((unsigned char *) frag +
|
||||
sizeof(struct s_ipv6_fragment),
|
||||
payload, FRAGMENT_LEN);
|
||||
|
||||
/* send translated packet */
|
||||
transmit_raw(packet, sizeof(struct s_ethernet) +
|
||||
sizeof(struct s_ipv6) +
|
||||
sizeof(struct s_ipv6_fragment) +
|
||||
FRAGMENT_LEN);
|
||||
|
||||
/* create the second fragment */
|
||||
ip6->len = htons(payload_size +
|
||||
sizeof(struct s_ipv6_fragment) -
|
||||
FRAGMENT_LEN);
|
||||
frag->offset_flag = htons((FRAGMENT_LEN / 8) << 3);
|
||||
|
||||
/* copy the payload data */
|
||||
memcpy((unsigned char *) frag +
|
||||
sizeof(struct s_ipv6_fragment),
|
||||
payload + FRAGMENT_LEN,
|
||||
payload_size - FRAGMENT_LEN);
|
||||
|
||||
/* send translated packet */
|
||||
transmit_raw(packet, sizeof(struct s_ethernet) +
|
||||
sizeof(struct s_ipv6) +
|
||||
sizeof(struct s_ipv6_fragment) -
|
||||
FRAGMENT_LEN + payload_size);
|
||||
} else {
|
||||
ip6->len = htons(payload_size);
|
||||
ip6->next_header = IPPROTO_TCP;
|
||||
|
||||
/* copy the payload data */
|
||||
memcpy((unsigned char *) ip6 + sizeof(struct s_ipv6),
|
||||
payload, payload_size);
|
||||
|
||||
/* send translated packet */
|
||||
transmit_raw(packet, sizeof(struct s_ethernet) +
|
||||
sizeof(struct s_ipv6) + payload_size);
|
||||
}
|
||||
} else {
|
||||
/* TODO: handle all fragments */
|
||||
printf("[Debug] Can't handle fragments :c(\n");
|
||||
return 1;
|
||||
}
|
||||
|
||||
/* allocate memory for translated packet */
|
||||
if ((packet = (unsigned char *) malloc(sizeof(struct s_ethernet) +
|
||||
sizeof(struct s_ipv6) +
|
||||
payload_size)) == NULL) {
|
||||
fprintf(stderr, "[Error] Lack of free memory\n");
|
||||
return 1;
|
||||
}
|
||||
eth6 = (struct s_ethernet *) packet;
|
||||
ip6 = (struct s_ipv6 *) (packet + sizeof(struct s_ethernet));
|
||||
|
||||
/* build ethernet header */
|
||||
eth6->dest = connection->mac;
|
||||
eth6->src = mac;
|
||||
eth6->type = htons(ETHERTYPE_IPV6);
|
||||
|
||||
/* build IPv6 packet */
|
||||
ip6->ver = 0x60;
|
||||
ip6->traffic_class = 0x0;
|
||||
ip6->flow_label = 0x0;
|
||||
ip6->len = htons(payload_size);
|
||||
ip6->next_header = IPPROTO_TCP;
|
||||
ip6->hop_limit = ip4->ttl;
|
||||
ipv4_to_ipv6(&ip4->ip_src, &ip6->ip_src);
|
||||
memcpy(&ip6->ip_dest, &connection->ipv6, sizeof(struct s_ipv6_addr));
|
||||
|
||||
/* set incoming source port */
|
||||
tcp->port_dest = connection->ipv6_port_src;
|
||||
|
||||
/* compute TCP checksum */
|
||||
tcp->checksum = checksum_ipv6_update(tcp->checksum,
|
||||
ip4->ip_src, ip4->ip_dest,
|
||||
connection->ipv4_port_src,
|
||||
ip6->ip_src, ip6->ip_dest,
|
||||
connection->ipv6_port_src);
|
||||
|
||||
/* copy the payload data (with new checksum) */
|
||||
memcpy(packet + sizeof(struct s_ethernet) + sizeof(struct s_ipv6),
|
||||
payload, payload_size);
|
||||
|
||||
/* send translated packet */
|
||||
transmit_raw(packet, sizeof(struct s_ethernet) + sizeof(struct s_ipv6) +
|
||||
payload_size);
|
||||
|
||||
/* clean-up */
|
||||
free(packet);
|
||||
|
||||
|
||||
@ -22,6 +22,8 @@
|
||||
#include "ipv4.h"
|
||||
#include "ipv6.h"
|
||||
|
||||
#define MTU 1280
|
||||
|
||||
extern struct ifreq interface;
|
||||
extern struct s_mac_addr mac;
|
||||
extern struct s_ipv6_addr ndp_multicast_addr;
|
||||
|
||||
Loading…
Reference in New Issue
Block a user