bool nat64_determine_incoming_tuple(struct sk_buff *skb, struct nf_conntrack_tuple **result)
{
struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
enum ip_conntrack_dir dir;
struct nf_conntrack_tuple *tuple;
log_debug("Step 1: Determining the Incoming Tuple");
// Conntrack already built the tuple, so just ask.
ct = nf_ct_get(skb, &ctinfo);
if (ct == NULL) {
log_warning(" Packet does not contain a conntrack entry. Dropping...");
return false;
}
dir = CTINFO2DIR(ctinfo);
tuple = &ct->tuplehash[dir].tuple;
log_tuple(tuple);
// Now perform the only validation defined in this step.
switch (tuple->l3_protocol) {
case NFPROTO_IPV4:
if (!is_l4_protocol_supported_ipv4(tuple->l4_protocol)) {
icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PROT_UNREACH, 0);
goto unsupported_l4_protocol;
}
break;
case NFPROTO_IPV6:
if (!is_l4_protocol_supported_ipv6(tuple->l4_protocol)) {
icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0);
goto unsupported_l4_protocol;
}
break;
default:
goto unsupported_l3_protocol;
}
*result = tuple;
log_debug("Done step 1.");
return true;
unsupported_l3_protocol:
log_warning(" Unsupported L3 protocol (%u). Dropping packet...", tuple->l3_protocol);
return false;
unsupported_l4_protocol:
log_warning(" Unsupported L4 protocol (%u). Dropping packet...", tuple->l4_protocol);
return false;
}
static bool test_address_filtering_aux(int src_addr_id, int src_port_id, int dst_addr_id,
int dst_port_id)
{
struct tuple tuple4;
tuple4.src.addr4.l3 = addr4[src_addr_id].l3;
tuple4.dst.addr4.l3 = addr4[dst_addr_id].l3;
tuple4.src.addr4.l4 = addr4[src_port_id].l4;
tuple4.dst.addr4.l4 = addr4[dst_port_id].l4;
tuple4.l4_proto = L4PROTO_UDP;
tuple4.l3_proto = L3PROTO_IPV4;
log_tuple(&tuple4);
return sessiondb_allow(&tuple4);
}
bool determine_in_tuple(struct sk_buff *skb, struct tuple *tuple)
{
struct iphdr *hdr4;
struct ipv6hdr *hdr6;
struct icmphdr *icmp4;
struct icmp6hdr *icmp6;
struct hdr_iterator iterator;
log_debug("Step 1: Determining the Incoming Tuple");
switch (be16_to_cpu(skb->protocol)) {
case ETH_P_IP:
hdr4 = ip_hdr(skb);
switch (hdr4->protocol) {
case IPPROTO_UDP:
if (!ipv4_udp(hdr4, ipv4_extract_l4_hdr(hdr4), tuple))
return false;
break;
case IPPROTO_TCP:
if (!ipv4_tcp(hdr4, ipv4_extract_l4_hdr(hdr4), tuple))
return false;
break;
case IPPROTO_ICMP:
icmp4 = ipv4_extract_l4_hdr(hdr4);
if (is_icmp4_info(icmp4->type)) {
if (!ipv4_icmp_info(hdr4, icmp4, tuple))
return false;
} else {
if (!ipv4_icmp_err(hdr4, icmp4, tuple))
return false;
}
break;
default:
log_info("Unsupported transport protocol for IPv4: %d.", hdr4->protocol);
icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PROT_UNREACH, 0);
return false;
}
break;
case ETH_P_IPV6:
hdr6 = ipv6_hdr(skb);
hdr_iterator_init(&iterator, hdr6);
hdr_iterator_last(&iterator);
switch (iterator.hdr_type) {
case IPPROTO_UDP:
if (!ipv6_udp(hdr6, iterator.data, tuple))
return false;
break;
case IPPROTO_TCP:
if (!ipv6_tcp(hdr6, iterator.data, tuple))
return false;
break;
case IPPROTO_ICMPV6:
icmp6 = iterator.data;
if (is_icmp6_info(icmp6->icmp6_type)) {
if (!ipv6_icmp_info(hdr6, icmp6, tuple))
return false;
} else {
if (!ipv6_icmp_err(hdr6, icmp6, tuple))
return false;
}
break;
default:
log_info("Unsupported transport protocol for IPv6: %d.", iterator.hdr_type);
icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0);
return false;
}
break;
default:
log_info("Packet's protocol (%d) is not IPv4 or IPv6.", be16_to_cpu(skb->protocol));
return false;
}
log_tuple(tuple);
log_debug("Done step 1.");
return true;
}
verdict compute_out_tuple(struct tuple *in, struct tuple *out, struct packet *pkt_in)
{
struct session_entry *session;
int error;
log_debug("Step 3: Computing the Outgoing Tuple");
error = sessiondb_get(in, &session);
if (error) {
/*
* Bogus ICMP errors might cause this because Filtering never cares for them,
* so it's not critical.
*/
log_debug("Error code %d while trying to find the packet's session entry.", error);
inc_stats(pkt_in, IPSTATS_MIB_INNOROUTES);
return VERDICT_DROP;
}
/*
* Though the end result is the same, the following section of code collides with the RFC
* in a superfluous sense.
*
* If the IPv6 pool has multiple prefixes, algorithmically generating addresses at this point
* is pointless because, in order to do that, we'd need to know which prefix was used when the
* session was created. This bit of information would have to be extracted from the session.
* However, the address already algorithmically generated also belongs to the session.
* So why bother generating it again? Just copy it.
*
* Additionally, the RFC wants some information extracted from the BIB entry.
* We *also* extract that information from the session because it's the same, by definition.
*
* And finally, the RFC wants some information extracted from the tuple.
* Same deal. If you draw all the scenarios (weirdass ICMP errors included), it's always the
* same as the session.
*
* Given all of that, I really don't understand why the RFC bothers with any of this, including
* making a distinction between 3-tuples and 5-tuples. The outgoing tuple is always a copy of
* the other side of the session, plain and simple. When you think about it, that last claim
* makes sense even in a general sense.
*/
switch (in->l3_proto) {
case L3PROTO_IPV6:
out->l3_proto = L3PROTO_IPV4;
out->l4_proto = in->l4_proto;
out->src.addr4 = session->local4;
out->dst.addr4 = session->remote4;
break;
case L3PROTO_IPV4:
out->l3_proto = L3PROTO_IPV6;
out->l4_proto = in->l4_proto;
out->src.addr6 = session->local6;
out->dst.addr6 = session->remote6;
break;
}
session_return(session);
log_tuple(out);
log_debug("Done step 3.");
return VERDICT_CONTINUE;
}
/**
* Extracts relevant data from "skb" and stores it in the "tuple" tuple.
*
* @param skb packet the data will be extracted from.
* @param tuple this function will populate this value using "skb"'s contents.
* @return whether packet processing should continue.
*/
verdict determine_in_tuple(struct sk_buff *skb, struct tuple *in_tuple)
{
struct icmphdr *icmp4;
struct icmp6hdr *icmp6;
verdict result = VER_CONTINUE;
log_debug("Step 1: Determining the Incoming Tuple");
switch (skb_l3_proto(skb)) {
case L3PROTO_IPV4:
switch (skb_l4_proto(skb)) {
case L4PROTO_UDP:
result = ipv4_udp(skb, in_tuple);
break;
case L4PROTO_TCP:
result = ipv4_tcp(skb, in_tuple);
break;
case L4PROTO_ICMP:
icmp4 = icmp_hdr(skb);
if (is_icmp4_info(icmp4->type)) {
result = ipv4_icmp_info(skb, in_tuple);
} else if (is_icmp4_error(icmp4->type)) {
result = ipv4_icmp_err(skb, in_tuple);
} else {
log_debug("Unknown ICMPv4 type: %u. Dropping packet...", icmp4->type);
inc_stats(skb, IPSTATS_MIB_INHDRERRORS);
result = VER_DROP;
}
break;
}
break;
case L3PROTO_IPV6:
switch (skb_l4_proto(skb)) {
case L4PROTO_UDP:
result = ipv6_udp(skb, in_tuple);
break;
case L4PROTO_TCP:
result = ipv6_tcp(skb, in_tuple);
break;
case L4PROTO_ICMP:
icmp6 = icmp6_hdr(skb);
if (is_icmp6_info(icmp6->icmp6_type)) {
result = ipv6_icmp_info(skb, in_tuple);
} else if (is_icmp6_error(icmp6->icmp6_type)) {
result = ipv6_icmp_err(skb, in_tuple);
} else {
log_debug("Unknown ICMPv6 type: %u. Dropping packet...", icmp6->icmp6_type);
inc_stats(skb, IPSTATS_MIB_INHDRERRORS);
result = VER_DROP;
}
break;
}
break;
}
/*
* We moved the transport-protocol-not-recognized ICMP errors to packet.c because they're
* covered in validations.
*/
log_tuple(in_tuple);
log_debug("Done step 1.");
return result;
}
/**
* Extracts relevant data from "frag" and stores it in the "tuple" tuple.
*
* @param frag fragment the data will be extracted from. Whether the packet is fragmented or not,
* this has to be the chunk whose fragment offset is zero.
* @param tuple this function will populate this value using "frag"'s contents.
* @return whether packet processing should continue.
*/
verdict determine_in_tuple(struct fragment *frag, struct tuple *tuple)
{
struct iphdr *hdr4;
struct ipv6hdr *hdr6;
struct icmphdr *icmp4;
struct icmp6hdr *icmp6;
verdict result = VER_CONTINUE;
log_debug("Step 1: Determining the Incoming Tuple");
switch (frag->l3_hdr.proto) {
case L3PROTO_IPV4:
hdr4 = frag_get_ipv4_hdr(frag);
switch (frag->l4_hdr.proto) {
case L4PROTO_UDP:
result = ipv4_udp(hdr4, frag_get_udp_hdr(frag), tuple);
break;
case L4PROTO_TCP:
result = ipv4_tcp(hdr4, frag_get_tcp_hdr(frag), tuple);
break;
case L4PROTO_ICMP:
icmp4 = frag_get_icmp4_hdr(frag);
if (is_icmp4_info(icmp4->type)) {
result = ipv4_icmp_info(hdr4, icmp4, tuple);
} else if (is_icmp4_error(icmp4->type)) {
result = ipv4_icmp_err(hdr4, icmp4, tuple);
} else {
log_warning("Unknown ICMPv4 type: %u. Dropping packet...", icmp4->type);
result = VER_DROP;
}
break;
case L4PROTO_NONE:
log_crit(ERR_ILLEGAL_NONE, "IPv4 - First fragment has no transport header.");
result = VER_DROP;
}
break;
case L3PROTO_IPV6:
hdr6 = frag_get_ipv6_hdr(frag);
switch (frag->l4_hdr.proto) {
case L4PROTO_UDP:
result = ipv6_udp(hdr6, frag_get_udp_hdr(frag), tuple);
break;
case L4PROTO_TCP:
result = ipv6_tcp(hdr6, frag_get_tcp_hdr(frag), tuple);
break;
case L4PROTO_ICMP:
icmp6 = frag_get_icmp6_hdr(frag);
if (is_icmp6_info(icmp6->icmp6_type)) {
result = ipv6_icmp_info(hdr6, icmp6, tuple);
} else if (is_icmp6_error(icmp6->icmp6_type)) {
result = ipv6_icmp_err(hdr6, icmp6, tuple);
} else {
log_warning("Unknown ICMPv6 type: %u. Dropping packet...", icmp6->icmp6_type);
result = VER_DROP;
}
break;
case L4PROTO_NONE:
log_crit(ERR_ILLEGAL_NONE, "IPv6 - First fragment has no transport header.");
result = VER_DROP;
}
break;
}
/*
* We moved the transport-protocol-not-recognized ICMP errors to fragment_db because they're
* covered in validations.
*/
log_tuple(tuple);
log_debug("Done step 1.");
return result;
}