forked from mirrors/linux
net/tcp: Verify inbound TCP-AO signed segments
Now there is a common function to verify signature on TCP segments:
tcp_inbound_hash(). It has checks for all possible cross-interactions
with MD5 signs as well as with unsigned segments.
The rules from RFC5925 are:
(1) Any TCP segment can have at max only one signature.
(2) TCP connections can't switch between using TCP-MD5 and TCP-AO.
(3) TCP-AO connections can't stop using AO, as well as unsigned
connections can't suddenly start using AO.
Co-developed-by: Francesco Ruggeri <fruggeri@arista.com>
Signed-off-by: Francesco Ruggeri <fruggeri@arista.com>
Co-developed-by: Salam Noureddine <noureddine@arista.com>
Signed-off-by: Salam Noureddine <noureddine@arista.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Acked-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Dmitry Safonov
David S. Miller
parent
9427c6aa3e
commit
0a3a809089
8 changed files with 248 additions and 47 deletions
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@ -24,6 +24,10 @@
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FN(TCP_MD5NOTFOUND) \
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FN(TCP_MD5UNEXPECTED) \
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FN(TCP_MD5FAILURE) \
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FN(TCP_AONOTFOUND) \
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FN(TCP_AOUNEXPECTED) \
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FN(TCP_AOKEYNOTFOUND) \
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FN(TCP_AOFAILURE) \
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FN(SOCKET_BACKLOG) \
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FN(TCP_FLAGS) \
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FN(TCP_ZEROWINDOW) \
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@ -163,6 +167,19 @@ enum skb_drop_reason {
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* to LINUX_MIB_TCPMD5FAILURE
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*/
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SKB_DROP_REASON_TCP_MD5FAILURE,
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/**
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* @SKB_DROP_REASON_TCP_AONOTFOUND: no TCP-AO hash and one was expected
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*/
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SKB_DROP_REASON_TCP_AONOTFOUND,
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/**
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* @SKB_DROP_REASON_TCP_AOUNEXPECTED: TCP-AO hash is present and it
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* was not expected.
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*/
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SKB_DROP_REASON_TCP_AOUNEXPECTED,
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/** @SKB_DROP_REASON_TCP_AOKEYNOTFOUND: TCP-AO key is unknown */
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SKB_DROP_REASON_TCP_AOKEYNOTFOUND,
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/** @SKB_DROP_REASON_TCP_AOFAILURE: TCP-AO hash is wrong */
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SKB_DROP_REASON_TCP_AOFAILURE,
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/**
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* @SKB_DROP_REASON_SOCKET_BACKLOG: failed to add skb to socket backlog (
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* see LINUX_MIB_TCPBACKLOGDROP)
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@ -1809,7 +1809,7 @@ tcp_md5_do_lookup_any_l3index(const struct sock *sk,
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enum skb_drop_reason
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tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
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const void *saddr, const void *daddr,
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int family, int dif, int sdif);
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int family, int l3index, const __u8 *hash_location);
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#define tcp_twsk_md5_key(twsk) ((twsk)->tw_md5_key)
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@ -1831,7 +1831,7 @@ tcp_md5_do_lookup_any_l3index(const struct sock *sk,
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static inline enum skb_drop_reason
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tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
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const void *saddr, const void *daddr,
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int family, int dif, int sdif)
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int family, int l3index, const __u8 *hash_location)
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{
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return SKB_NOT_DROPPED_YET;
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}
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@ -2730,4 +2730,53 @@ static inline bool tcp_ao_required(struct sock *sk, const void *saddr,
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return false;
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}
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/* Called with rcu_read_lock() */
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static inline enum skb_drop_reason
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tcp_inbound_hash(struct sock *sk, const struct request_sock *req,
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const struct sk_buff *skb,
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const void *saddr, const void *daddr,
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int family, int dif, int sdif)
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{
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const struct tcphdr *th = tcp_hdr(skb);
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const struct tcp_ao_hdr *aoh;
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const __u8 *md5_location;
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int l3index;
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/* Invalid option or two times meet any of auth options */
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if (tcp_parse_auth_options(th, &md5_location, &aoh))
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return SKB_DROP_REASON_TCP_AUTH_HDR;
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if (req) {
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if (tcp_rsk_used_ao(req) != !!aoh)
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return SKB_DROP_REASON_TCP_AOFAILURE;
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}
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/* sdif set, means packet ingressed via a device
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* in an L3 domain and dif is set to the l3mdev
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*/
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l3index = sdif ? dif : 0;
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/* Fast path: unsigned segments */
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if (likely(!md5_location && !aoh)) {
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/* Drop if there's TCP-MD5 or TCP-AO key with any rcvid/sndid
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* for the remote peer. On TCP-AO established connection
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* the last key is impossible to remove, so there's
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* always at least one current_key.
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*/
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if (tcp_ao_required(sk, saddr, family))
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return SKB_DROP_REASON_TCP_AONOTFOUND;
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if (unlikely(tcp_md5_do_lookup(sk, l3index, saddr, family))) {
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NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5NOTFOUND);
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return SKB_DROP_REASON_TCP_MD5NOTFOUND;
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}
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return SKB_NOT_DROPPED_YET;
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}
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if (aoh)
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return tcp_inbound_ao_hash(sk, skb, family, req, aoh);
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return tcp_inbound_md5_hash(sk, skb, saddr, daddr, family,
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l3index, md5_location);
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}
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#endif /* _TCP_H */
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@ -111,6 +111,9 @@ struct tcp6_ao_context {
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};
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struct tcp_sigpool;
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#define TCP_AO_ESTABLISHED (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_FIN_WAIT2 | \
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TCPF_CLOSE | TCPF_CLOSE_WAIT | \
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TCPF_LAST_ACK | TCPF_CLOSING)
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int tcp_ao_transmit_skb(struct sock *sk, struct sk_buff *skb,
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struct tcp_ao_key *key, struct tcphdr *th,
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@ -130,6 +133,10 @@ int tcp_ao_calc_traffic_key(struct tcp_ao_key *mkt, u8 *key, void *ctx,
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unsigned int len, struct tcp_sigpool *hp);
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void tcp_ao_destroy_sock(struct sock *sk, bool twsk);
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void tcp_ao_time_wait(struct tcp_timewait_sock *tcptw, struct tcp_sock *tp);
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enum skb_drop_reason tcp_inbound_ao_hash(struct sock *sk,
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const struct sk_buff *skb, unsigned short int family,
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const struct request_sock *req,
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const struct tcp_ao_hdr *aoh);
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struct tcp_ao_key *tcp_ao_do_lookup(const struct sock *sk,
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const union tcp_ao_addr *addr,
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int family, int sndid, int rcvid);
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@ -208,6 +215,13 @@ static inline void tcp_ao_syncookie(struct sock *sk, const struct sk_buff *skb,
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{
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}
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static inline enum skb_drop_reason tcp_inbound_ao_hash(struct sock *sk,
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const struct sk_buff *skb, unsigned short int family,
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const struct request_sock *req, const struct tcp_ao_hdr *aoh)
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{
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return SKB_NOT_DROPPED_YET;
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}
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static inline struct tcp_ao_key *tcp_ao_do_lookup(const struct sock *sk,
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const union tcp_ao_addr *addr, int family, int sndid, int rcvid)
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{
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@ -4375,42 +4375,23 @@ EXPORT_SYMBOL(tcp_md5_hash_key);
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enum skb_drop_reason
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tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
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const void *saddr, const void *daddr,
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int family, int dif, int sdif)
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int family, int l3index, const __u8 *hash_location)
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{
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/*
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* This gets called for each TCP segment that arrives
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* so we want to be efficient.
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/* This gets called for each TCP segment that has TCP-MD5 option.
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* We have 3 drop cases:
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* o No MD5 hash and one expected.
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* o MD5 hash and we're not expecting one.
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* o MD5 hash and its wrong.
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*/
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const __u8 *hash_location = NULL;
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struct tcp_md5sig_key *hash_expected;
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const struct tcphdr *th = tcp_hdr(skb);
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const struct tcp_sock *tp = tcp_sk(sk);
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int genhash, l3index;
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struct tcp_md5sig_key *key;
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u8 newhash[16];
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int genhash;
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/* sdif set, means packet ingressed via a device
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* in an L3 domain and dif is set to the l3mdev
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*/
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l3index = sdif ? dif : 0;
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key = tcp_md5_do_lookup(sk, l3index, saddr, family);
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hash_expected = tcp_md5_do_lookup(sk, l3index, saddr, family);
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if (tcp_parse_auth_options(th, &hash_location, NULL))
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return SKB_DROP_REASON_TCP_AUTH_HDR;
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/* We've parsed the options - do we have a hash? */
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if (!hash_expected && !hash_location)
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return SKB_NOT_DROPPED_YET;
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if (hash_expected && !hash_location) {
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NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5NOTFOUND);
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return SKB_DROP_REASON_TCP_MD5NOTFOUND;
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}
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if (!hash_expected && hash_location) {
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if (!key && hash_location) {
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NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5UNEXPECTED);
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return SKB_DROP_REASON_TCP_MD5UNEXPECTED;
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}
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@ -4420,14 +4401,10 @@ tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
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* IPv4-mapped case.
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*/
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if (family == AF_INET)
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genhash = tcp_v4_md5_hash_skb(newhash,
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hash_expected,
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NULL, skb);
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genhash = tcp_v4_md5_hash_skb(newhash, key, NULL, skb);
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else
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genhash = tp->af_specific->calc_md5_hash(newhash,
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hash_expected,
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genhash = tp->af_specific->calc_md5_hash(newhash, key,
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NULL, skb);
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if (genhash || memcmp(hash_location, newhash, 16) != 0) {
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NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5FAILURE);
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if (family == AF_INET) {
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@ -761,6 +761,148 @@ void tcp_ao_syncookie(struct sock *sk, const struct sk_buff *skb,
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treq->maclen = tcp_ao_maclen(key);
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}
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static enum skb_drop_reason
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tcp_ao_verify_hash(const struct sock *sk, const struct sk_buff *skb,
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unsigned short int family, struct tcp_ao_info *info,
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const struct tcp_ao_hdr *aoh, struct tcp_ao_key *key,
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u8 *traffic_key, u8 *phash, u32 sne)
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{
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u8 maclen = aoh->length - sizeof(struct tcp_ao_hdr);
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const struct tcphdr *th = tcp_hdr(skb);
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void *hash_buf = NULL;
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if (maclen != tcp_ao_maclen(key))
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return SKB_DROP_REASON_TCP_AOFAILURE;
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hash_buf = kmalloc(tcp_ao_digest_size(key), GFP_ATOMIC);
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if (!hash_buf)
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return SKB_DROP_REASON_NOT_SPECIFIED;
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/* XXX: make it per-AF callback? */
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tcp_ao_hash_skb(family, hash_buf, key, sk, skb, traffic_key,
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(phash - (u8 *)th), sne);
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if (memcmp(phash, hash_buf, maclen)) {
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kfree(hash_buf);
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return SKB_DROP_REASON_TCP_AOFAILURE;
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}
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kfree(hash_buf);
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return SKB_NOT_DROPPED_YET;
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}
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enum skb_drop_reason
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tcp_inbound_ao_hash(struct sock *sk, const struct sk_buff *skb,
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unsigned short int family, const struct request_sock *req,
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const struct tcp_ao_hdr *aoh)
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{
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const struct tcphdr *th = tcp_hdr(skb);
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u8 *phash = (u8 *)(aoh + 1); /* hash goes just after the header */
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struct tcp_ao_info *info;
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enum skb_drop_reason ret;
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struct tcp_ao_key *key;
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__be32 sisn, disn;
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u8 *traffic_key;
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u32 sne = 0;
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info = rcu_dereference(tcp_sk(sk)->ao_info);
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if (!info)
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return SKB_DROP_REASON_TCP_AOUNEXPECTED;
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if (unlikely(th->syn)) {
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sisn = th->seq;
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disn = 0;
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}
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/* Fast-path */
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if (likely((1 << sk->sk_state) & TCP_AO_ESTABLISHED)) {
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enum skb_drop_reason err;
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struct tcp_ao_key *current_key;
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/* Check if this socket's rnext_key matches the keyid in the
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* packet. If not we lookup the key based on the keyid
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* matching the rcvid in the mkt.
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*/
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key = READ_ONCE(info->rnext_key);
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if (key->rcvid != aoh->keyid) {
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key = tcp_ao_established_key(info, -1, aoh->keyid);
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if (!key)
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goto key_not_found;
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}
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/* Delayed retransmitted SYN */
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if (unlikely(th->syn && !th->ack))
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goto verify_hash;
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sne = 0;
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/* Established socket, traffic key are cached */
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traffic_key = rcv_other_key(key);
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err = tcp_ao_verify_hash(sk, skb, family, info, aoh, key,
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traffic_key, phash, sne);
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if (err)
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return err;
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current_key = READ_ONCE(info->current_key);
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/* Key rotation: the peer asks us to use new key (RNext) */
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if (unlikely(aoh->rnext_keyid != current_key->sndid)) {
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/* If the key is not found we do nothing. */
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key = tcp_ao_established_key(info, aoh->rnext_keyid, -1);
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if (key)
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/* pairs with tcp_ao_del_cmd */
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WRITE_ONCE(info->current_key, key);
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}
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return SKB_NOT_DROPPED_YET;
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}
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/* Lookup key based on peer address and keyid.
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* current_key and rnext_key must not be used on tcp listen
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* sockets as otherwise:
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* - request sockets would race on those key pointers
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* - tcp_ao_del_cmd() allows async key removal
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*/
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key = tcp_ao_inbound_lookup(family, sk, skb, -1, aoh->keyid);
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if (!key)
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goto key_not_found;
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if (th->syn && !th->ack)
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goto verify_hash;
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if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_NEW_SYN_RECV)) {
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/* Make the initial syn the likely case here */
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if (unlikely(req)) {
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sne = 0;
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sisn = htonl(tcp_rsk(req)->rcv_isn);
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disn = htonl(tcp_rsk(req)->snt_isn);
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} else if (unlikely(th->ack && !th->syn)) {
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/* Possible syncookie packet */
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sisn = htonl(ntohl(th->seq) - 1);
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disn = htonl(ntohl(th->ack_seq) - 1);
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sne = 0;
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} else if (unlikely(!th->syn)) {
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/* no way to figure out initial sisn/disn - drop */
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return SKB_DROP_REASON_TCP_FLAGS;
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}
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} else if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
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disn = info->lisn;
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if (th->syn || th->rst)
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sisn = th->seq;
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else
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sisn = info->risn;
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} else {
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WARN_ONCE(1, "TCP-AO: Unexpected sk_state %d", sk->sk_state);
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return SKB_DROP_REASON_TCP_AOFAILURE;
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}
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verify_hash:
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traffic_key = kmalloc(tcp_ao_digest_size(key), GFP_ATOMIC);
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if (!traffic_key)
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return SKB_DROP_REASON_NOT_SPECIFIED;
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tcp_ao_calc_key_skb(key, traffic_key, skb, sisn, disn, family);
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ret = tcp_ao_verify_hash(sk, skb, family, info, aoh, key,
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traffic_key, phash, sne);
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kfree(traffic_key);
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return ret;
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key_not_found:
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return SKB_DROP_REASON_TCP_AOKEYNOTFOUND;
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}
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static int tcp_ao_cache_traffic_keys(const struct sock *sk,
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struct tcp_ao_info *ao,
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struct tcp_ao_key *ao_key)
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|
|
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@ -2204,7 +2204,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
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if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
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drop_reason = SKB_DROP_REASON_XFRM_POLICY;
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else
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drop_reason = tcp_inbound_md5_hash(sk, skb,
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drop_reason = tcp_inbound_hash(sk, req, skb,
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&iph->saddr, &iph->daddr,
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AF_INET, dif, sdif);
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if (unlikely(drop_reason)) {
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@ -2283,8 +2283,8 @@ int tcp_v4_rcv(struct sk_buff *skb)
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goto discard_and_relse;
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}
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drop_reason = tcp_inbound_md5_hash(sk, skb, &iph->saddr,
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&iph->daddr, AF_INET, dif, sdif);
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drop_reason = tcp_inbound_hash(sk, NULL, skb, &iph->saddr, &iph->daddr,
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AF_INET, dif, sdif);
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if (drop_reason)
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goto discard_and_relse;
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|
|
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@ -56,8 +56,9 @@ int tcp_v6_ao_calc_key_skb(struct tcp_ao_key *mkt, u8 *key,
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const struct ipv6hdr *iph = ipv6_hdr(skb);
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const struct tcphdr *th = tcp_hdr(skb);
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|
||||
return tcp_v6_ao_calc_key(mkt, key, &iph->saddr, &iph->daddr,
|
||||
th->source, th->dest, sisn, disn);
|
||||
return tcp_v6_ao_calc_key(mkt, key, &iph->saddr,
|
||||
&iph->daddr, th->source,
|
||||
th->dest, sisn, disn);
|
||||
}
|
||||
|
||||
int tcp_v6_ao_calc_key_sk(struct tcp_ao_key *mkt, u8 *key,
|
||||
|
|
|
|||
|
|
@ -1785,7 +1785,7 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
|
|||
if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
|
||||
drop_reason = SKB_DROP_REASON_XFRM_POLICY;
|
||||
else
|
||||
drop_reason = tcp_inbound_md5_hash(sk, skb,
|
||||
drop_reason = tcp_inbound_hash(sk, req, skb,
|
||||
&hdr->saddr, &hdr->daddr,
|
||||
AF_INET6, dif, sdif);
|
||||
if (drop_reason) {
|
||||
|
|
@ -1861,7 +1861,7 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
|
|||
goto discard_and_relse;
|
||||
}
|
||||
|
||||
drop_reason = tcp_inbound_md5_hash(sk, skb, &hdr->saddr, &hdr->daddr,
|
||||
drop_reason = tcp_inbound_hash(sk, NULL, skb, &hdr->saddr, &hdr->daddr,
|
||||
AF_INET6, dif, sdif);
|
||||
if (drop_reason)
|
||||
goto discard_and_relse;
|
||||
|
|
@ -2089,6 +2089,7 @@ static const struct tcp_sock_af_ops tcp_sock_ipv6_mapped_specific = {
|
|||
.ao_lookup = tcp_v6_ao_lookup,
|
||||
.calc_ao_hash = tcp_v4_ao_hash_skb,
|
||||
.ao_parse = tcp_v6_parse_ao,
|
||||
.ao_calc_key_sk = tcp_v4_ao_calc_key_sk,
|
||||
#endif
|
||||
};
|
||||
#endif
|
||||
|
|
|
|||
Loading…
Reference in a new issue