tcp: add support for TCP over UDP

Adding support for TCP over UDP allows communication with
TCP stacks which can be implemented in userspace without
requiring special priviledges or specific support by the OS.
This is joint work with rrs.

Reviewed by:		rrs
Sponsored by:		Netflix, Inc.
MFC after:		1 week
Differential Revision:	https://reviews.freebsd.org/D29469

1 files changed, 24 insertions, 3 deletions

diff --git a/sys/netinet/tcp_var.h b/sys/netinet/tcp_var.h
index 4d28cab80d89..dfd2f239d007 100644
--- a/sys/netinet/tcp_var.h
+++ b/sys/netinet/tcp_var.h
@@ -282,6 +282,16 @@ struct tcptemp {
 	struct	tcphdr tt_t;
 };
 
+/* Enable TCP/UDP tunneling port */
+#define TCP_TUNNELING_PORT_MIN		0
+#define TCP_TUNNELING_PORT_MAX		65535
+#define TCP_TUNNELING_PORT_DEFAULT	0
+
+/* Enable TCP/UDP tunneling port */
+#define TCP_TUNNELING_OVERHEAD_MIN	sizeof(struct udphdr)
+#define TCP_TUNNELING_OVERHEAD_MAX	1024
+#define TCP_TUNNELING_OVERHEAD_DEFAULT	TCP_TUNNELING_OVERHEAD_MIN
+
 /* Minimum map entries limit value, if set */
 #define TCP_MIN_MAP_ENTRIES_LIMIT	128
 
@@ -502,6 +512,8 @@ struct in_conninfo;
 
 struct tcptw {
 	struct inpcb	*tw_inpcb;	/* XXX back pointer to internet pcb */
+	uint32_t  t_port:16,		/* UDP port number if TCPoUDP */
+		t_unused:16;
 	tcp_seq		snd_nxt;
 	tcp_seq		rcv_nxt;
 	tcp_seq		iss;
@@ -678,7 +690,10 @@ struct	tcpstat {
 	uint64_t tcps_pmtud_blackhole_activated_min_mss; /* BH at min MSS Count */
 	uint64_t tcps_pmtud_blackhole_failed;		 /* Black Hole Failure Count */
 
-	uint64_t _pad[12];		/* 6 UTO, 6 TBD */
+	uint64_t tcps_tunneled_pkts;	/* Packets encap's in UDP received */
+	uint64_t tcps_tunneled_errs;	/* Packets that had errors that were UDP encaped */
+
+	uint64_t _pad[10];		/* 6 UTO, 6 TBD */
 };
 
 #define	tcps_rcvmemdrop	tcps_rcvreassfull	/* compat */
@@ -776,7 +791,9 @@ struct xtcpcb {
 	uint32_t	t_rcv_wnd;		/* (s) */
 	uint32_t	t_snd_wnd;		/* (s) */
 	uint32_t	xt_ecn;			/* (s) */
-	int32_t		spare32[26];
+	uint16_t	xt_encaps_port;		/* (s) */
+	int16_t		spare16;
+	int32_t		spare32[25];
 } __aligned(8);
 
 #ifdef _KERNEL
@@ -867,6 +884,8 @@ VNET_DECLARE(int, tcp_sack_globalmaxholes);
 VNET_DECLARE(int, tcp_sack_maxholes);
 VNET_DECLARE(int, tcp_sc_rst_sock_fail);
 VNET_DECLARE(int, tcp_sendspace);
+VNET_DECLARE(int, tcp_udp_tunneling_overhead);
+VNET_DECLARE(int, tcp_udp_tunneling_port);
 VNET_DECLARE(struct inpcbhead, tcb);
 VNET_DECLARE(struct inpcbinfo, tcbinfo);
 
@@ -929,6 +948,7 @@ void	 tcp_twstart(struct tcpcb *);
 void	 tcp_twclose(struct tcptw *, int);
 void	 tcp_ctlinput(int, struct sockaddr *, void *);
 int	 tcp_ctloutput(struct socket *, struct sockopt *);
+void 	 tcp_ctlinput_viaudp(int, struct sockaddr *, void *, void *);
 struct tcpcb *
 	 tcp_drop(struct tcpcb *, int);
 void	 tcp_drain(void);
@@ -963,6 +983,7 @@ void	hhook_run_tcp_est_in(struct tcpcb *tp,
 int	 tcp_input(struct mbuf **, int *, int);
 int	 tcp_autorcvbuf(struct mbuf *, struct tcphdr *, struct socket *,
 	    struct tcpcb *, int);
+int	 tcp_input_with_port(struct mbuf **, int *, int, uint16_t);
 void	 tcp_handle_wakeup(struct tcpcb *, struct socket *);
 void	 tcp_do_segment(struct mbuf *, struct tcphdr *,
 			struct socket *, struct tcpcb *, int, int, uint8_t);
@@ -1033,7 +1054,7 @@ void	 tcp_setpersist(struct tcpcb *);
 void	 tcp_slowtimo(void);
 struct tcptemp *
 	 tcpip_maketemplate(struct inpcb *);
-void	 tcpip_fillheaders(struct inpcb *, void *, void *);
+void	 tcpip_fillheaders(struct inpcb *, uint16_t, void *, void *);
 void	 tcp_timer_activate(struct tcpcb *, uint32_t, u_int);
 int	 tcp_timer_suspend(struct tcpcb *, uint32_t);
 void	 tcp_timers_unsuspend(struct tcpcb *, uint32_t);