/**
* Attempts to find "tuple"'s BIB entry and returns it in "bib".
* Assumes "tuple" represents a IPv4 packet.
*/
static int get_bib_ipv4(struct packet *pkt, struct tuple *tuple4, struct bib_entry **bib)
{
int error;
error = bibdb_get(tuple4, bib);
if (error) {
if (error == -ESRCH) {
log_debug("There is no BIB entry for the incoming IPv4 packet.");
inc_stats(pkt, IPSTATS_MIB_INNOROUTES);
} else {
log_debug("Error code %d while finding a BIB entry for the incoming packet.", error);
inc_stats(pkt, IPSTATS_MIB_INDISCARDS);
icmp64_send(pkt, ICMPERR_ADDR_UNREACHABLE, 0);
}
return error;
}
if (config_get_addr_dependent_filtering() && !sessiondb_allow(tuple4)) {
log_debug("Packet was blocked by address-dependent filtering.");
icmp64_send(pkt, ICMPERR_FILTER, 0);
inc_stats(pkt, IPSTATS_MIB_INDISCARDS);
bib_return(*bib);
return -EPERM;
}
return 0;
}
static int whine_if_too_big(struct packet *in, struct packet *out)
{
unsigned int len;
unsigned int mtu;
if (pkt_l3_proto(in) == L3PROTO_IPV4 && !is_dont_fragment_set(pkt_ip4_hdr(in)))
return 0;
len = pkt_len(out);
mtu = get_nexthop_mtu(out);
if (len > mtu) {
/*
* We don't have to worry about ICMP errors causing this because the translate code already
* truncates them.
*/
log_debug("Packet is too big (len: %u, mtu: %u).", len, mtu);
switch (pkt_l3_proto(out)) {
case L3PROTO_IPV6:
mtu -= 20;
break;
case L3PROTO_IPV4:
mtu += 20;
break;
}
icmp64_send(out, ICMPERR_FRAG_NEEDED, mtu);
return -EINVAL;
}
return 0;
}
/**
* Second half of the filtering and updating done during the CLOSED state of the TCP state machine.
* Processes IPv4 SYN packets when there's no state.
* Part of RFC 6146 section 3.5.2.2.
*/
static verdict tcp_closed_v4_syn(struct packet *pkt, struct tuple *tuple4)
{
struct bib_entry *bib;
struct session_entry *session;
int error;
verdict result = VERDICT_DROP;
if (config_get_drop_external_connections()) {
log_debug("Applying policy: Dropping externally initiated TCP connections.");
return VERDICT_DROP;
}
error = bibdb_get(tuple4, &bib);
if (error) {
if (error != -ESRCH)
return VERDICT_DROP;
bib = NULL;
}
log_bib(bib);
error = create_session_ipv4(tuple4, bib, &session);
if (error)
goto end_bib;
log_session(session);
session->state = V4_INIT;
if (!bib || config_get_addr_dependent_filtering()) {
error = pktqueue_add(session, pkt);
if (error) {
if (error == -E2BIG) {
/* Fall back to assume there's no Simultaneous Open. */
icmp64_send(pkt, ICMPERR_PORT_UNREACHABLE, 0);
}
goto end_session;
}
/* At this point, skb's original skb completely belongs to pktqueue. */
result = VERDICT_STOLEN;
error = sessiondb_add(session, SESSIONTIMER_SYN);
if (error) {
log_debug("Error code %d while adding the session to the DB.", error);
pktqueue_remove(session);
goto end_session;
}
} else {
error = sessiondb_add(session, SESSIONTIMER_TRANS);
if (error) {
log_debug("Error code %d while adding the session to the DB.", error);
goto end_session;
}
result = VERDICT_CONTINUE;
}
/* Fall through. */
end_session:
session_return(session);
/* Fall through. */
end_bib:
if (bib)
bib_return(bib);
return result;
}
