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This fixes several bugs that Larry Rosenman helped me find in

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Rack with respect to its handling of TCP Fast Open. Several
fixes all related to TFO are included in this commit:
1) Handling of non-TFO retransmissions
2) Building the proper send-map when we are doing TFO
3) Dealing with the ack that comes back that includes the
   SYN and data.

It appears that with this commit TFO now works :-)

Thanks Larry for all your help!!

Sponsored by:	Netflix Inc.
Differential Revision:	https://reviews.freebsd.org/D15758
This commit is contained in:
Randall Stewart 2018-06-14 03:27:42 +00:00
parent ae19b2ef9b
commit 4aec110f70
1 changed files with 111 additions and 57 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

162
sys/netinet/tcp_stacks/rack.c
View File

@ -2083,6 +2083,8 @@ rack_timer_start(struct tcpcb *tp, struct tcp_rack *rack, uint32_t cts)
/* We can't start any timer in persists */
return (rack_get_persists_timer_val(tp, rack));
}
if (tp->t_state < TCPS_ESTABLISHED)
goto activate_rxt;
rsm = TAILQ_FIRST(&rack->r_ctl.rc_tmap);
if (rsm == NULL) {
/* Nothing on the send map */
@ -3385,8 +3387,15 @@ rack_log_output(struct tcpcb *tp, struct tcpopt *to, int32_t len,
rsm->r_tim_lastsent[0] = ts;
rsm->r_rtr_cnt = 1;
rsm->r_rtr_bytes = 0;
if (th_flags & TH_SYN) {
/* The data space is one beyond snd_una */
rsm->r_start = seq_out + 1;
rsm->r_end = rsm->r_start + (len - 1);
} else {
/* Normal case */
rsm->r_start = seq_out;
rsm->r_end = rsm->r_start + len;
}
rsm->r_sndcnt = 0;
TAILQ_INSERT_TAIL(&rack->r_ctl.rc_map, rsm, r_next);
TAILQ_INSERT_TAIL(&rack->r_ctl.rc_tmap, rsm, r_tnext);
@ -4657,11 +4666,7 @@ rack_process_data(struct mbuf *m, struct tcphdr *th, struct socket *so,
* send garbage on first SYN.
*/
int32_t nsegs;
#ifdef TCP_RFC7413
int32_t tfo_syn;
#else
#define tfo_syn (FALSE)
#endif
struct tcp_rack *rack;
rack = (struct tcp_rack *)tp->t_fb_ptr;
@ -4767,10 +4772,8 @@ rack_process_data(struct mbuf *m, struct tcphdr *th, struct socket *so,
* PRU_RCVD). If a FIN has already been received on this connection
* then we just ignore the text.
*/
#ifdef TCP_RFC7413
tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) &&
(tp->t_flags & TF_FASTOPEN));
#endif
IS_FASTOPEN(tp->t_flags));
if ((tlen || (thflags & TH_FIN) || tfo_syn) &&
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
tcp_seq save_start = th->th_seq;
@ -5237,6 +5240,8 @@ rack_do_syn_sent(struct mbuf *m, struct tcphdr *th, struct socket *so,
tp->irs = th->th_seq;
tcp_rcvseqinit(tp);
if (thflags & TH_ACK) {
int tfo_partial = 0;
TCPSTAT_INC(tcps_connects);
soisconnected(so);
#ifdef MAC
@ -5249,11 +5254,20 @@ rack_do_syn_sent(struct mbuf *m, struct tcphdr *th, struct socket *so,
}
tp->rcv_adv += min(tp->rcv_wnd,
TCP_MAXWIN << tp->rcv_scale);
/*
* If not all the data that was sent in the TFO SYN
* has been acked, resend the remainder right away.
*/
if (IS_FASTOPEN(tp->t_flags) &&
(tp->snd_una != tp->snd_max)) {
tp->snd_nxt = th->th_ack;
tfo_partial = 1;
}
/*
* If there's data, delay ACK; if there's also a FIN ACKNOW
* will be turned on later.
*/
if (DELAY_ACK(tp, tlen) && tlen != 0) {
if (DELAY_ACK(tp, tlen) && tlen != 0 && (tfo_partial == 0)) {
rack_timer_cancel(tp, (struct tcp_rack *)tp->t_fb_ptr,
((struct tcp_rack *)tp->t_fb_ptr)->r_ctl.rc_rcvtime, __LINE__);
tp->t_flags |= TF_DELACK;
@ -5266,6 +5280,21 @@ rack_do_syn_sent(struct mbuf *m, struct tcphdr *th, struct socket *so,
tp->t_flags |= TF_ECN_PERMIT;
TCPSTAT_INC(tcps_ecn_shs);
}
if (SEQ_GT(th->th_ack, tp->snd_una)) {
/*
* We advance snd_una for the
* fast open case. If th_ack is
* acknowledging data beyond
* snd_una we can't just call
* ack-processing since the
* data stream in our send-map
* will start at snd_una + 1 (one
* beyond the SYN). If its just
* equal we don't need to do that
* and there is no send_map.
*/
tp->snd_una++;
}
/*
* Received <SYN,ACK> in SYN_SENT[*] state. Transitions:
* SYN_SENT --> ESTABLISHED SYN_SENT* --> FIN_WAIT_1
@ -5375,13 +5404,13 @@ rack_do_syn_recv(struct mbuf *m, struct tcphdr *th, struct socket *so,
rack_do_dropwithreset(m, tp, th, ti_locked, BANDLIM_RST_OPENPORT, tlen);
return (1);
}
#ifdef TCP_RFC7413
if (tp->t_flags & TF_FASTOPEN) {
if (IS_FASTOPEN(tp->t_flags)) {
/*
* When a TFO connection is in SYN_RECEIVED, the only valid
* packets are the initial SYN, a retransmit/copy of the
* initial SYN (possibly with a subset of the original
* data), a valid ACK, a FIN, or a RST.
* When a TFO connection is in SYN_RECEIVED, the
* only valid packets are the initial SYN, a
* retransmit/copy of the initial SYN (possibly with
* a subset of the original data), a valid ACK, a
* FIN, or a RST.
*/
if ((thflags & (TH_SYN | TH_ACK)) == (TH_SYN | TH_ACK)) {
rack_do_dropwithreset(m, tp, th, ti_locked, BANDLIM_RST_OPENPORT, tlen);
@ -5402,7 +5431,6 @@ rack_do_syn_recv(struct mbuf *m, struct tcphdr *th, struct socket *so,
return (0);
}
}
#endif
if (thflags & TH_RST)
return (rack_process_rst(m, th, so, tp, ti_locked));
/*
@ -5463,12 +5491,10 @@ rack_do_syn_recv(struct mbuf *m, struct tcphdr *th, struct socket *so,
* processing; else drop segment and return.
*/
if ((thflags & TH_ACK) == 0) {
#ifdef TCP_RFC7413
if (tp->t_flags & TF_FASTOPEN) {
if (IS_FASTOPEN(tp->t_flags)) {
tp->snd_wnd = tiwin;
cc_conn_init(tp);
}
#endif
return (rack_process_data(m, th, so, tp, drop_hdrlen, tlen,
ti_locked, tiwin, thflags, nxt_pkt));
}
@ -5492,8 +5518,7 @@ rack_do_syn_recv(struct mbuf *m, struct tcphdr *th, struct socket *so,
tcp_state_change(tp, TCPS_ESTABLISHED);
TCP_PROBE5(accept__established, NULL, tp,
mtod(m, const char *), tp, th);
#ifdef TCP_RFC7413
if (tp->t_tfo_pending) {
if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) {
tcp_fastopen_decrement_counter(tp->t_tfo_pending);
tp->t_tfo_pending = NULL;
@ -5509,8 +5534,7 @@ rack_do_syn_recv(struct mbuf *m, struct tcphdr *th, struct socket *so,
* is not harmless as it would undo the snd_cwnd reduction
* that occurs when a TFO SYN|ACK is retransmitted.
*/
if (!(tp->t_flags & TF_FASTOPEN))
#endif
if (!IS_FASTOPEN(tp->t_flags))
cc_conn_init(tp);
}
/*
@ -6926,6 +6950,7 @@ rack_output(struct tcpcb *tp)
struct tcp_rack *rack;
struct tcphdr *th;
uint8_t pass = 0;
uint8_t wanted_cookie = 0;
u_char opt[TCP_MAXOLEN];
unsigned ipoptlen, optlen, hdrlen, ulen=0;
uint32_t rack_seq;
@ -6967,17 +6992,15 @@ rack_output(struct tcpcb *tp)
return (tcp_offload_output(tp));
#endif
#ifdef TCP_RFC7413
/*
* For TFO connections in SYN_RECEIVED, only allow the initial
* SYN|ACK and those sent by the retransmit timer.
*/
if ((tp->t_flags & TF_FASTOPEN) &&
if (IS_FASTOPEN(tp->t_flags) &&
(tp->t_state == TCPS_SYN_RECEIVED) &&
SEQ_GT(tp->snd_max, tp->snd_una) && /* inital SYN|ACK sent */
(tp->snd_nxt != tp->snd_una)) /* not a retransmit */
SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN|ACK sent */
(rack->r_ctl.rc_resend == NULL)) /* not a retransmit */
return (0);
#endif
#ifdef INET6
if (rack->r_state) {
/* Use the cache line loaded if possible */
@ -7267,7 +7290,7 @@ rack_output(struct tcpcb *tp)
uint32_t avail;
avail = sbavail(sb);
if (SEQ_GT(tp->snd_nxt, tp->snd_una))
if (SEQ_GT(tp->snd_nxt, tp->snd_una) && avail)
sb_offset = tp->snd_nxt - tp->snd_una;
else
sb_offset = 0;
@ -7359,22 +7382,18 @@ rack_output(struct tcpcb *tp)
* SYN-SENT state and if segment contains data and if we don't know
* that foreign host supports TAO, suppress sending segment.
*/
if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
if ((tp->t_state != TCPS_SYN_RECEIVED) &&
(tp->t_state != TCPS_SYN_SENT))
if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una) &&
((sack_rxmit == 0) && (tp->t_rxtshift == 0))) {
if (tp->t_state != TCPS_SYN_RECEIVED)
flags &= ~TH_SYN;
#ifdef TCP_RFC7413
/*
* When sending additional segments following a TFO SYN|ACK,
* do not include the SYN bit.
*/
if ((tp->t_flags & TF_FASTOPEN) &&
if (IS_FASTOPEN(tp->t_flags) &&
(tp->t_state == TCPS_SYN_RECEIVED))
flags &= ~TH_SYN;
#endif
sb_offset--, len++;
if (sbavail(sb) == 0)
len = 0;
}
/*
* Be careful not to send data and/or FIN on SYN segments. This
@ -7385,16 +7404,27 @@ rack_output(struct tcpcb *tp)
len = 0;
flags &= ~TH_FIN;
}
#ifdef TCP_RFC7413
/*
* When retransmitting SYN|ACK on a passively-created TFO socket,
* don't include data, as the presence of data may have caused the
* original SYN|ACK to have been dropped by a middlebox.
* On TFO sockets, ensure no data is sent in the following cases:
*
* - When retransmitting SYN|ACK on a passively-created socket
*
* - When retransmitting SYN on an actively created socket
*
* - When sending a zero-length cookie (cookie request) on an
* actively created socket
*
* - When the socket is in the CLOSED state (RST is being sent)
*/
if ((tp->t_flags & TF_FASTOPEN) &&
((tp->t_state == TCPS_SYN_RECEIVED) && (tp->t_rxtshift > 0)))
if (IS_FASTOPEN(tp->t_flags) &&
(((flags & TH_SYN) && (tp->t_rxtshift > 0)) ||
((tp->t_state == TCPS_SYN_SENT) &&
(tp->t_tfo_client_cookie_len == 0)) ||
(flags & TH_RST)))
len = 0;
/* Without fast-open there should never be data sent on a SYN */
if ((flags & TH_SYN) && (!IS_FASTOPEN(tp->t_flags)))
len = 0;
#endif
if (len <= 0) {
/*
* If FIN has been sent but not acked, but we haven't been
@ -7710,22 +7740,39 @@ rack_output(struct tcpcb *tp)
to.to_mss -= V_tcp_udp_tunneling_overhead;
#endif
to.to_flags |= TOF_MSS;
#ifdef TCP_RFC7413
/*
* Only include the TFO option on the first
* transmission of the SYN|ACK on a
* passively-created TFO socket, as the presence of
* the TFO option may have caused the original
* SYN|ACK to have been dropped by a middlebox.
* On SYN or SYN|ACK transmits on TFO connections,
* only include the TFO option if it is not a
* retransmit, as the presence of the TFO option may
* have caused the original SYN or SYN|ACK to have
* been dropped by a middlebox.
*/
if ((tp->t_flags & TF_FASTOPEN) &&
(tp->t_state == TCPS_SYN_RECEIVED) &&
if (IS_FASTOPEN(tp->t_flags) &&
(tp->t_rxtshift == 0)) {
to.to_tfo_len = TCP_FASTOPEN_MAX_COOKIE_LEN;
to.to_tfo_cookie = (u_char *)&tp->t_tfo_cookie;
if (tp->t_state == TCPS_SYN_RECEIVED) {
to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN;
to.to_tfo_cookie =
(u_int8_t *)&tp->t_tfo_cookie.server;
to.to_flags |= TOF_FASTOPEN;
wanted_cookie = 1;
} else if (tp->t_state == TCPS_SYN_SENT) {
to.to_tfo_len =
tp->t_tfo_client_cookie_len;
to.to_tfo_cookie =
tp->t_tfo_cookie.client;
to.to_flags |= TOF_FASTOPEN;
wanted_cookie = 1;
/*
* If we wind up having more data to
* send with the SYN than can fit in
* one segment, don't send any more
* until the SYN|ACK comes back from
* the other end.
*/
sendalot = 0;
}
}
#endif
}
/* Window scaling. */
if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) {
@ -7760,6 +7807,13 @@ rack_output(struct tcpcb *tp)
/* Processing the options. */
hdrlen += optlen = tcp_addoptions(&to, opt);
/*
* If we wanted a TFO option to be added, but it was unable
* to fit, ensure no data is sent.
*/
if (IS_FASTOPEN(tp->t_flags) && wanted_cookie &&
!(to.to_flags & TOF_FASTOPEN))
len = 0;
}
#ifdef NETFLIX_TCPOUDP
if (tp->t_port) {