static struct sock *dccp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
{
const struct dccp_hdr *dh = dccp_hdr(skb);
const struct iphdr *iph = ip_hdr(skb);
struct sock *nsk;
struct request_sock **prev;
/* Find possible connection requests. */
struct request_sock *req = inet_csk_search_req(sk, &prev,
dh->dccph_sport,
iph->saddr, iph->daddr);
if (req != NULL)
return dccp_check_req(sk, skb, req, prev);
nsk = inet_lookup_established(sock_net(sk), &dccp_hashinfo,
iph->saddr, dh->dccph_sport,
iph->daddr, dh->dccph_dport,
inet_iif(skb));
if (nsk != NULL) {
if (nsk->sk_state != DCCP_TIME_WAIT) {
bh_lock_sock(nsk);
return nsk;
}
inet_twsk_put(inet_twsk(nsk));
return NULL;
}
return sk;
}
/* Similar to: tcp_v4_do_rcv
* We only process join requests here. (either the SYN or the final ACK)
*/
int mptcp_v4_do_rcv(struct sock *meta_sk, struct sk_buff *skb)
{
const struct tcphdr *th = tcp_hdr(skb);
const struct iphdr *iph = ip_hdr(skb);
struct sock *child, *rsk = NULL, *sk;
int ret;
sk = inet_lookup_established(sock_net(meta_sk), &tcp_hashinfo,
iph->saddr, th->source, iph->daddr,
th->dest, inet_iif(skb));
if (!sk)
goto new_subflow;
if (is_meta_sk(sk)) {
WARN("%s Did not find a sub-sk - did found the meta!\n", __func__);
sock_put(sk);
goto discard;
}
if (sk->sk_state == TCP_TIME_WAIT) {
inet_twsk_put(inet_twsk(sk));
goto discard;
}
if (sk->sk_state == TCP_NEW_SYN_RECV) {
struct request_sock *req = inet_reqsk(sk);
bool req_stolen;
if (!mptcp_can_new_subflow(meta_sk))
goto reset_and_discard;
local_bh_disable();
child = tcp_check_req(meta_sk, skb, req, false, &req_stolen);
if (!child) {
reqsk_put(req);
local_bh_enable();
goto discard;
}
if (child != meta_sk) {
ret = mptcp_finish_handshake(child, skb);
if (ret) {
rsk = child;
local_bh_enable();
goto reset_and_discard;
}
local_bh_enable();
return 0;
}
/* tcp_check_req failed */
reqsk_put(req);
local_bh_enable();
goto discard;
}
ret = tcp_v4_do_rcv(sk, skb);
sock_put(sk);
return ret;
new_subflow:
if (!mptcp_can_new_subflow(meta_sk))
goto reset_and_discard;
child = tcp_v4_cookie_check(meta_sk, skb);
if (!child)
goto discard;
if (child != meta_sk) {
ret = mptcp_finish_handshake(child, skb);
if (ret) {
rsk = child;
goto reset_and_discard;
}
}
if (tcp_hdr(skb)->syn) {
local_bh_disable();
mptcp_v4_join_request(meta_sk, skb);
local_bh_enable();
}
discard:
kfree_skb(skb);
return 0;
reset_and_discard:
tcp_v4_send_reset(rsk, skb);
goto discard;
}