On Feb 22, 2005, at 23:38, Baruch Even wrote:
We have a version of ABC (Appropriate Byte Counting) implementation of
RFC 3465, which we hope to submit soon for inclusion in the kernel
which should be a more appropriate solution for this. The RFC is a
well defined standard whereas this patch has not received any
reviewing by the networking community.
Please find enclosed a version of our implementation of RFC3465 ABC for
Linux 2.6.11-rc4.
There is in-built protection, as defined by the RFC, to prevent large
bursts of packets should acks arrive acknowledging more than abc_L
packets (sysctl_tcp_abc_L). The entire abc patch can be switched on or
off using sysctl_tcp_abc={1|0} respectively. As this is also a RFT, it
is switched ON by default and has the abc_L value of 2 which MAY be
used (according to the RFC).
Note that an abc_L of 1 will be more conservative than what is
available with normal clocking of delayed acks. Note that there is
currently no built in mechanism to prevent abc_L being set to over 2;
the RFC defines that abc_L MUST NOT be greater than 2.
This patch also has the advantage of working for all protocols
currently in the kernel (except vegas which doesn't require it).
Signed-off-by: Yee-Ting Li <Yee-Ting.Li@xxxxxx>
Index: linux-2.6.11-rc4/include/linux/sysctl.h
===================================================================
--- linux-2.6.11-rc4.orig/include/linux/sysctl.h Sun Feb 13 03:06:53
2005
+++ linux-2.6.11-rc4/include/linux/sysctl.h Tue Feb 22 23:48:30 2005
@@ -344,6 +344,8 @@
NET_TCP_DEFAULT_WIN_SCALE=105,
NET_TCP_MODERATE_RCVBUF=106,
NET_TCP_TSO_WIN_DIVISOR=107,
+ NET_TCP_ABC=108,
+ NET_TCP_ABC_L=109,
};
enum {
Index: linux-2.6.11-rc4/include/linux/tcp.h
===================================================================
--- linux-2.6.11-rc4.orig/include/linux/tcp.h Sun Feb 13 03:06:23 2005
+++ linux-2.6.11-rc4/include/linux/tcp.h Tue Feb 22 23:39:41 2005
@@ -366,6 +366,8 @@
__u32 total_retrans; /* Total retransmits for entire connection */
+ __u32 bytes_acked; /* Appropiate Byte Counting - RFC3465 */
+
/* The syn_wait_lock is necessary only to avoid proc interface having
* to grab the main lock sock while browsing the listening hash
* (otherwise it's deadlock prone).
Index: linux-2.6.11-rc4/include/net/tcp.h
===================================================================
--- linux-2.6.11-rc4.orig/include/net/tcp.h Sun Feb 13 03:05:28 2005
+++ linux-2.6.11-rc4/include/net/tcp.h Tue Feb 22 23:47:59 2005
@@ -609,6 +609,10 @@
extern int sysctl_tcp_moderate_rcvbuf;
extern int sysctl_tcp_tso_win_divisor;
+/* RFC3465 - ABC */
+extern int sysctl_tcp_abc;
+extern int sysctl_tcp_abc_L;
+
extern atomic_t tcp_memory_allocated;
extern atomic_t tcp_sockets_allocated;
extern int tcp_memory_pressure;
@@ -1366,6 +1370,7 @@
static inline void tcp_enter_cwr(struct tcp_sock *tp)
{
tp->prior_ssthresh = 0;
+ tp->bytes_acked=0;
if (tp->ca_state < TCP_CA_CWR) {
__tcp_enter_cwr(tp);
tcp_set_ca_state(tp, TCP_CA_CWR);
Index: linux-2.6.11-rc4/net/ipv4/sysctl_net_ipv4.c
===================================================================
--- linux-2.6.11-rc4.orig/net/ipv4/sysctl_net_ipv4.c Sun Feb 13
03:07:01 2005
+++ linux-2.6.11-rc4/net/ipv4/sysctl_net_ipv4.c Tue Feb 22 23:46:18 2005
@@ -682,6 +682,22 @@
.mode = 0644,
.proc_handler = &proc_dointvec,
},
+ {
+ .ctl_name = NET_TCP_ABC,
+ .procname = "tcp_abc",
+ .data = &sysctl_tcp_abc,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec,
+ },
+ {
+ .ctl_name = NET_TCP_ABC_L,
+ .procname = "tcp_abc_L",
+ .data = &sysctl_tcp_abc_L,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec,
+ },
{ .ctl_name = 0 }
};
Index: linux-2.6.11-rc4/net/ipv4/tcp.c
===================================================================
--- linux-2.6.11-rc4.orig/net/ipv4/tcp.c Sun Feb 13 03:05:50 2005
+++ linux-2.6.11-rc4/net/ipv4/tcp.c Tue Feb 22 23:28:28 2005
@@ -1825,6 +1825,7 @@
tp->packets_out = 0;
tp->snd_ssthresh = 0x7fffffff;
tp->snd_cwnd_cnt = 0;
+ tp->bytes_acked = 0;
tcp_set_ca_state(tp, TCP_CA_Open);
tcp_clear_retrans(tp);
tcp_delack_init(tp);
Index: linux-2.6.11-rc4/net/ipv4/tcp_input.c
===================================================================
--- linux-2.6.11-rc4.orig/net/ipv4/tcp_input.c Tue Feb 22 23:27:44 2005
+++ linux-2.6.11-rc4/net/ipv4/tcp_input.c Wed Feb 23 00:25:44 2005
@@ -92,6 +92,11 @@
int sysctl_tcp_moderate_rcvbuf = 1;
+/* RFC 3465 - ABC */
+int sysctl_tcp_abc = 1;
+int sysctl_tcp_abc_L = 2; /* The RFC definess 1 as being a more
conservative value */
+ /* that SHOULD be used, however, we use 2 as it MAY
be used */
+
/* Default values of the Vegas variables, in fixed-point representation
* with V_PARAM_SHIFT bits to the right of the binary point.
*/
@@ -1287,6 +1292,7 @@
tp->snd_cwnd_cnt = 0;
tp->snd_cwnd_stamp = tcp_time_stamp;
+ tp->bytes_acked = 0;
tcp_clear_retrans(tp);
/* Push undo marker, if it was plain RTO and nothing
@@ -1945,6 +1951,8 @@
TCP_ECN_queue_cwr(tp);
}
+ tp->bytes_acked = 0;
+
tp->snd_cwnd_cnt = 0;
tcp_set_ca_state(tp, TCP_CA_Recovery);
}
@@ -2100,6 +2108,24 @@
tp->snd_cwnd_stamp = tcp_time_stamp;
}
+/* This is a wrapper function to handle RFC3465 - ABC. As per the RFC,
the abc_L
+ * value defines a burst moderation to prevent sending large bursts of
packets
+ * should an ack acknowledge many packets. abc_L MUST NOT be larger
than 2. */
+static __inline__ void reno_cong_avoid_abc( struct tcp_sock *tp, int
mss_now )
+{
+ int incrs_applied = 0;
+
+ if (sysctl_tcp_abc && !tp->nonagle)
+ {
+ while (tp->bytes_acked > mss_now && incrs_applied <
sysctl_tcp_abc_L) {
+ tp->bytes_acked -= mss_now;
+ reno_cong_avoid( tp );
+ }
+ } else
+ reno_cong_avoid( tp );
+}
+
+
/* This is based on the congestion detection/avoidance scheme
described in
* Lawrence S. Brakmo and Larry L. Peterson.
* "TCP Vegas: End to end congestion avoidance on a global
internet."
@@ -2322,12 +2348,15 @@
tp->snd_cwnd_stamp = tcp_time_stamp;
}
-static inline void tcp_cong_avoid(struct tcp_sock *tp, u32 ack, u32
seq_rtt)
+static inline void tcp_cong_avoid(struct sock *sk, u32 ack, u32
seq_rtt)
{
+ struct tcp_sock *tp = tcp_sk(sk);
+ int mss_now = tcp_current_mss(sk,1);
+
if (tcp_vegas_enabled(tp))
vegas_cong_avoid(tp, ack, seq_rtt);
else
- reno_cong_avoid(tp);
+ reno_cong_avoid_abc(tp, mss_now);
}
/* Restart timer after forward progress on connection.
@@ -2890,6 +2919,9 @@
if (before(ack, prior_snd_una))
goto old_ack;
+ if ( sysctl_tcp_abc && tp->ca_state < TCP_CA_CWR )
+ tp->bytes_acked += ack - prior_snd_una;
+
if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
/* Window is constant, pure forward advance.
* No more checks are required.
@@ -2940,12 +2972,12 @@
if ((flag & FLAG_DATA_ACKED) &&
(tcp_vegas_enabled(tp) || prior_in_flight >= tp->snd_cwnd)
&&
tcp_may_raise_cwnd(tp, flag))
- tcp_cong_avoid(tp, ack, seq_rtt);
+ tcp_cong_avoid(sk, ack, seq_rtt);
tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag);
} else {
if ((flag & FLAG_DATA_ACKED) &&
(tcp_vegas_enabled(tp) || prior_in_flight >= tp->snd_cwnd))
- tcp_cong_avoid(tp, ack, seq_rtt);
+ tcp_cong_avoid(sk, ack, seq_rtt);
}
if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP))
Index: linux-2.6.11-rc4/net/ipv4/tcp_minisocks.c
===================================================================
--- linux-2.6.11-rc4.orig/net/ipv4/tcp_minisocks.c Sun Feb 13 03:07:01
2005
+++ linux-2.6.11-rc4/net/ipv4/tcp_minisocks.c Tue Feb 22 23:28:28 2005
@@ -769,6 +769,8 @@
newtp->snd_cwnd = 2;
newtp->snd_cwnd_cnt = 0;
+ newtp->bytes_acked = 0;
+
newtp->frto_counter = 0;
newtp->frto_highmark = 0;
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