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tcp: Remove TCPCT

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TCPCT uses option-number 253, reserved for experimental use and should
not be used in production environments.
Further, TCPCT does not fully implement RFC 6013.

As a nice side-effect, removing TCPCT increases TCP's performance for
very short flows:

Doing an apache-benchmark with -c 100 -n 100000, sending HTTP-requests
for files of 1KB size.

before this patch:
	average (among 7 runs) of 20845.5 Requests/Second
after:
	average (among 7 runs) of 21403.6 Requests/Second

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Christoph Paasch
2013-03-17 08:23:34 +00:00
committed by David S. Miller
parent 94d8f2b133
commit 1a2c6181c4
18 changed files with 37 additions and 840 deletions
Download Patch File Download Diff File Expand all files Collapse all files

217
net/ipv4/tcp_output.c
View File

@@ -65,9 +65,6 @@ int sysctl_tcp_base_mss __read_mostly = TCP_BASE_MSS;
/* By default, RFC2861 behavior. */
int sysctl_tcp_slow_start_after_idle __read_mostly = 1;
int sysctl_tcp_cookie_size __read_mostly = 0; /* TCP_COOKIE_MAX */
EXPORT_SYMBOL_GPL(sysctl_tcp_cookie_size);
static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
int push_one, gfp_t gfp);
@@ -386,7 +383,6 @@ static inline bool tcp_urg_mode(const struct tcp_sock *tp)
#define OPTION_TS (1 << 1)
#define OPTION_MD5 (1 << 2)
#define OPTION_WSCALE (1 << 3)
#define OPTION_COOKIE_EXTENSION (1 << 4)
#define OPTION_FAST_OPEN_COOKIE (1 << 8)
struct tcp_out_options {
@@ -400,36 +396,6 @@ struct tcp_out_options {
struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */
};
/* The sysctl int routines are generic, so check consistency here.
*/
static u8 tcp_cookie_size_check(u8 desired)
{
int cookie_size;
if (desired > 0)
/* previously specified */
return desired;
cookie_size = ACCESS_ONCE(sysctl_tcp_cookie_size);
if (cookie_size <= 0)
/* no default specified */
return 0;
if (cookie_size <= TCP_COOKIE_MIN)
/* value too small, specify minimum */
return TCP_COOKIE_MIN;
if (cookie_size >= TCP_COOKIE_MAX)
/* value too large, specify maximum */
return TCP_COOKIE_MAX;
if (cookie_size & 1)
/* 8-bit multiple, illegal, fix it */
cookie_size++;
return (u8)cookie_size;
}
/* Write previously computed TCP options to the packet.
*
* Beware: Something in the Internet is very sensitive to the ordering of
@@ -448,27 +414,9 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
{
u16 options = opts->options; /* mungable copy */
/* Having both authentication and cookies for security is redundant,
* and there's certainly not enough room. Instead, the cookie-less
* extension variant is proposed.
*
* Consider the pessimal case with authentication. The options
* could look like:
* COOKIE|MD5(20) + MSS(4) + SACK|TS(12) + WSCALE(4) == 40
*/
if (unlikely(OPTION_MD5 & options)) {
if (unlikely(OPTION_COOKIE_EXTENSION & options)) {
*ptr++ = htonl((TCPOPT_COOKIE << 24) |
(TCPOLEN_COOKIE_BASE << 16) |
(TCPOPT_MD5SIG << 8) |
TCPOLEN_MD5SIG);
} else {
*ptr++ = htonl((TCPOPT_NOP << 24) |
(TCPOPT_NOP << 16) |
(TCPOPT_MD5SIG << 8) |
TCPOLEN_MD5SIG);
}
options &= ~OPTION_COOKIE_EXTENSION;
*ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
(TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
/* overload cookie hash location */
opts->hash_location = (__u8 *)ptr;
ptr += 4;
@@ -497,44 +445,6 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
*ptr++ = htonl(opts->tsecr);
}
/* Specification requires after timestamp, so do it now.
*
* Consider the pessimal case without authentication. The options
* could look like:
* MSS(4) + SACK|TS(12) + COOKIE(20) + WSCALE(4) == 40
*/
if (unlikely(OPTION_COOKIE_EXTENSION & options)) {
__u8 *cookie_copy = opts->hash_location;
u8 cookie_size = opts->hash_size;
/* 8-bit multiple handled in tcp_cookie_size_check() above,
* and elsewhere.
*/
if (0x2 & cookie_size) {
__u8 *p = (__u8 *)ptr;
/* 16-bit multiple */
*p++ = TCPOPT_COOKIE;
*p++ = TCPOLEN_COOKIE_BASE + cookie_size;
*p++ = *cookie_copy++;
*p++ = *cookie_copy++;
ptr++;
cookie_size -= 2;
} else {
/* 32-bit multiple */
*ptr++ = htonl(((TCPOPT_NOP << 24) |
(TCPOPT_NOP << 16) |
(TCPOPT_COOKIE << 8) |
TCPOLEN_COOKIE_BASE) +
cookie_size);
}
if (cookie_size > 0) {
memcpy(ptr, cookie_copy, cookie_size);
ptr += (cookie_size / 4);
}
}
if (unlikely(OPTION_SACK_ADVERTISE & options)) {
*ptr++ = htonl((TCPOPT_NOP << 24) |
(TCPOPT_NOP << 16) |
@@ -593,11 +503,7 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
struct tcp_md5sig_key **md5)
{
struct tcp_sock *tp = tcp_sk(sk);
struct tcp_cookie_values *cvp = tp->cookie_values;
unsigned int remaining = MAX_TCP_OPTION_SPACE;
u8 cookie_size = (!tp->rx_opt.cookie_out_never && cvp != NULL) ?
tcp_cookie_size_check(cvp->cookie_desired) :
0;
struct tcp_fastopen_request *fastopen = tp->fastopen_req;
#ifdef CONFIG_TCP_MD5SIG
@@ -649,52 +555,7 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
tp->syn_fastopen = 1;
}
}
/* Note that timestamps are required by the specification.
*
* Odd numbers of bytes are prohibited by the specification, ensuring
* that the cookie is 16-bit aligned, and the resulting cookie pair is
* 32-bit aligned.
*/
if (*md5 == NULL &&
(OPTION_TS & opts->options) &&
cookie_size > 0) {
int need = TCPOLEN_COOKIE_BASE + cookie_size;
if (0x2 & need) {
/* 32-bit multiple */
need += 2; /* NOPs */
if (need > remaining) {
/* try shrinking cookie to fit */
cookie_size -= 2;
need -= 4;
}
}
while (need > remaining && TCP_COOKIE_MIN <= cookie_size) {
cookie_size -= 4;
need -= 4;
}
if (TCP_COOKIE_MIN <= cookie_size) {
opts->options |= OPTION_COOKIE_EXTENSION;
opts->hash_location = (__u8 *)&cvp->cookie_pair[0];
opts->hash_size = cookie_size;
/* Remember for future incarnations. */
cvp->cookie_desired = cookie_size;
if (cvp->cookie_desired != cvp->cookie_pair_size) {
/* Currently use random bytes as a nonce,
* assuming these are completely unpredictable
* by hostile users of the same system.
*/
get_random_bytes(&cvp->cookie_pair[0],
cookie_size);
cvp->cookie_pair_size = cookie_size;
}
remaining -= need;
}
}
return MAX_TCP_OPTION_SPACE - remaining;
}
@@ -704,14 +565,10 @@ static unsigned int tcp_synack_options(struct sock *sk,
unsigned int mss, struct sk_buff *skb,
struct tcp_out_options *opts,
struct tcp_md5sig_key **md5,
struct tcp_extend_values *xvp,
struct tcp_fastopen_cookie *foc)
{
struct inet_request_sock *ireq = inet_rsk(req);
unsigned int remaining = MAX_TCP_OPTION_SPACE;
u8 cookie_plus = (xvp != NULL && !xvp->cookie_out_never) ?
xvp->cookie_plus :
0;
#ifdef CONFIG_TCP_MD5SIG
*md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);
@@ -759,28 +616,7 @@ static unsigned int tcp_synack_options(struct sock *sk,
remaining -= need;
}
}
/* Similar rationale to tcp_syn_options() applies here, too.
* If the <SYN> options fit, the same options should fit now!
*/
if (*md5 == NULL &&
ireq->tstamp_ok &&
cookie_plus > TCPOLEN_COOKIE_BASE) {
int need = cookie_plus; /* has TCPOLEN_COOKIE_BASE */
if (0x2 & need) {
/* 32-bit multiple */
need += 2; /* NOPs */
}
if (need <= remaining) {
opts->options |= OPTION_COOKIE_EXTENSION;
opts->hash_size = cookie_plus - TCPOLEN_COOKIE_BASE;
remaining -= need;
} else {
/* There's no error return, so flag it. */
xvp->cookie_out_never = 1; /* true */
opts->hash_size = 0;
}
}
return MAX_TCP_OPTION_SPACE - remaining;
}
@@ -2802,32 +2638,24 @@ int tcp_send_synack(struct sock *sk)
* sk: listener socket
* dst: dst entry attached to the SYNACK
* req: request_sock pointer
* rvp: request_values pointer
*
* Allocate one skb and build a SYNACK packet.
* @dst is consumed : Caller should not use it again.
*/
struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
struct request_sock *req,
struct request_values *rvp,
struct tcp_fastopen_cookie *foc)
{
struct tcp_out_options opts;
struct tcp_extend_values *xvp = tcp_xv(rvp);
struct inet_request_sock *ireq = inet_rsk(req);
struct tcp_sock *tp = tcp_sk(sk);
const struct tcp_cookie_values *cvp = tp->cookie_values;
struct tcphdr *th;
struct sk_buff *skb;
struct tcp_md5sig_key *md5;
int tcp_header_size;
int mss;
int s_data_desired = 0;
if (cvp != NULL && cvp->s_data_constant && cvp->s_data_desired)
s_data_desired = cvp->s_data_desired;
skb = alloc_skb(MAX_TCP_HEADER + 15 + s_data_desired,
sk_gfp_atomic(sk, GFP_ATOMIC));
skb = alloc_skb(MAX_TCP_HEADER + 15, sk_gfp_atomic(sk, GFP_ATOMIC));
if (unlikely(!skb)) {
dst_release(dst);
return NULL;
@@ -2869,9 +2697,8 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
else
#endif
TCP_SKB_CB(skb)->when = tcp_time_stamp;
tcp_header_size = tcp_synack_options(sk, req, mss,
skb, &opts, &md5, xvp, foc)
+ sizeof(*th);
tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, &md5,
foc) + sizeof(*th);
skb_push(skb, tcp_header_size);
skb_reset_transport_header(skb);
@@ -2889,40 +2716,6 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn,
TCPHDR_SYN | TCPHDR_ACK);
if (OPTION_COOKIE_EXTENSION & opts.options) {
if (s_data_desired) {
u8 *buf = skb_put(skb, s_data_desired);
/* copy data directly from the listening socket. */
memcpy(buf, cvp->s_data_payload, s_data_desired);
TCP_SKB_CB(skb)->end_seq += s_data_desired;
}
if (opts.hash_size > 0) {
__u32 workspace[SHA_WORKSPACE_WORDS];
u32 *mess = &xvp->cookie_bakery[COOKIE_DIGEST_WORDS];
u32 *tail = &mess[COOKIE_MESSAGE_WORDS-1];
/* Secret recipe depends on the Timestamp, (future)
* Sequence and Acknowledgment Numbers, Initiator
* Cookie, and others handled by IP variant caller.
*/
*tail-- ^= opts.tsval;
*tail-- ^= tcp_rsk(req)->rcv_isn + 1;
*tail-- ^= TCP_SKB_CB(skb)->seq + 1;
/* recommended */
*tail-- ^= (((__force u32)th->dest << 16) | (__force u32)th->source);
*tail-- ^= (u32)(unsigned long)cvp; /* per sockopt */
sha_transform((__u32 *)&xvp->cookie_bakery[0],
(char *)mess,
&workspace[0]);
opts.hash_location =
(__u8 *)&xvp->cookie_bakery[0];
}
}
th->seq = htonl(TCP_SKB_CB(skb)->seq);
/* XXX data is queued and acked as is. No buffer/window check */
th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);