hello! I haven't done any kernel-hacking before, so be patient.
I got as far as to make tcphealth run, but now I need some help:
how does read-locking work in the tcp_sock struct?
the original code (for 2.5.1) made a read_lock(&head->lock) with
struct tcp_ehash_bucket *head = &tcp_ehash[i];
at the beginning of the for-loop over all sk=head->chain.
i.e.
for (i=0; i < tcp_ehash_size; i++) {
struct tcp_ehash_bucket *head = &tcp_ehash[i];
struct sock *sk;
struct tcp_opt *tp;
read_lock(&head->lock);
for (sk=head->chain; sk; sk=sk->next) {
if (!TCP_INET_FAMILY(sk->family))
continue;
and in the new kernel this construction has been replaced by
if (st->state==TCP_SEQ_STATE_ESTABLISHED)
...
static struct tcp_seq_afinfo tcphealth_seq_afinfo
...
and the example with proc/net/tcp is seemingly not locking anything. do I
actually need a read-lock for diagnostic data from tcp_sock? why did the
original author need to lock the whole chain of tcp_sock?
here's my patch against 3.4.4 so far, any further comments welcome:
diff -rub linux-3.4.4/include/linux/tcp.h
linux-3.4.4-heal-lsm/include/linux/tcp.h
--- linux-3.4.4/include/linux/tcp.h 2012-06-22 20:37:50.000000000 +0200
+++ linux-3.4.4-heal-lsm/include/linux/tcp.h 2012-07-06 10:23:13.000000000
+0200
@@ -7,6 +7,8 @@
*
* Version: @(#)tcp.h 1.0.2 04/28/93
*
+ * Federico D. Sacerdoti : Added TCP health counters.
+ *
* Author: Fred N. van Kempen, <wal...@uwalt.nl.mugnet.org>
*
* This program is free software; you can redistribute it and/or
@@ -472,6 +474,15 @@
* contains related tcp_cookie_transactions fields.
*/
struct tcp_cookie_values *cookie_values;
+
+ /*
+ * TCP health monitoring counters.
+ */
+ __u32 dup_acks_sent;
+ __u32 dup_pkts_recv;
+ __u32 acks_sent;
+ __u32 pkts_recv;
+ __u32 last_ack_sent; /* Sequence number of the last ack we
sent. */
};
static inline struct tcp_sock *tcp_sk(const struct sock *sk)
diff -rub linux-3.4.4/net/ipv4/tcp_input.c
linux-3.4.4-heal-lsm/net/ipv4/tcp_input.c
--- linux-3.4.4/net/ipv4/tcp_input.c 2012-06-22 20:37:50.000000000 +0200
+++ linux-3.4.4-heal-lsm/net/ipv4/tcp_input.c 2012-07-06
10:12:12.000000000 +0200
@@ -59,7 +59,8 @@
* Panu Kuhlberg: Experimental audit of TCP
(re)transmission
* engine. Lots of bugs are found.
* Pasi Sarolahti: F-RTO for dealing with spurious RTOs
- */
+ * Federico D. Sacerdoti: Added TCP health monitoring.
+*/
#define pr_fmt(fmt) "TCP: " fmt
@@ -4414,6 +4415,8 @@
}
if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
+ /* Course retransmit inefficiency- this packet has been
received
twice. */
+ tp->dup_pkts_recv++;
SOCK_DEBUG(sk, "ofo packet was already received\n");
__skb_unlink(skb, &tp->out_of_order_queue);
__kfree_skb(skb);
@@ -4664,6 +4667,10 @@
return;
}
+ /* A packet is a "duplicate" if it contains bytes we have already
received. */
+ if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
+ tp->dup_pkts_recv++;
+
if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
/* A retransmit, 2nd most common case. Force an immediate ack.
*/
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
@@ -5375,6 +5382,14 @@
tp->rx_opt.saw_tstamp = 0;
+ /*
+ * Tcp health monitoring is interested in
+ * total per-connection packet arrivals.
+ * This is in the fast path, but is quick.
+ */
+
+ tp->pkts_recv++;
+
/* pred_flags is 0xS?10 << 16 + snd_wnd
* if header_prediction is to be made
* 'S' will always be tp->tcp_header_len >> 2
diff -rub linux-3.4.4/net/ipv4/tcp_ipv4.c
linux-3.4.4-heal-lsm/net/ipv4/tcp_ipv4.c
--- linux-3.4.4/net/ipv4/tcp_ipv4.c 2012-06-22 20:37:50.000000000 +0200
+++ linux-3.4.4-heal-lsm/net/ipv4/tcp_ipv4.c 2012-07-11 09:34:22.000000000
+0200
@@ -2533,6 +2533,82 @@
return 0;
}
+
+/*
+ * Output /proc/net/tcphealth
+ */
+#define LINESZ 128
+
+int tcp_health_seq_show(struct seq_file *seq, void *v)
+{
+ int len, num;
+ char srcIP[32], destIP[32];
+
+ unsigned long SmoothedRttEstimate,
+ AcksSent, DupAcksSent, PktsRecv, DupPktsRecv;
+ struct tcp_iter_state *st;
+
+ if (v == SEQ_START_TOKEN) {
+ seq_printf(seq,
+ "TCP Health Monitoring (established connections only)\n"
+ " -Duplicate ACKs indicate lost or reordered packets on the
connection.\n"
+ " -Duplicate Packets Received signal a slow and badly
inefficient
connection.\n"
+ " -RttEst estimates how long future packets will take on a
round trip
over the connection.\n"
+ "id Local Address Remote Address RttEst(ms)
AcksSent "
+ "DupAcksSent PktsRecv DupPktsRecv\n");
+ goto out;
+ }
+
+ /* Loop through established TCP connections */
+ st = seq->private;
+
+
+ if (st->state==TCP_SEQ_STATE_ESTABLISHED)
+ {
+/* ; //insert read-lock here */
+ const struct tcp_sock *tp = tcp_sk(v);
+ const struct inet_sock *inet = inet_sk(v);
+ __be32 dest = inet->inet_daddr;
+ __be32 src = inet->inet_rcv_saddr;
+ __u16 destp = ntohs(inet->inet_dport);
+ __u16 srcp = ntohs(inet->inet_sport);
+
+ num=st->num;
+ SmoothedRttEstimate = (tp->srtt >> 3);
+ AcksSent = tp->acks_sent;
+ DupAcksSent = tp->dup_acks_sent;
+ PktsRecv = tp->pkts_recv;
+ DupPktsRecv = tp->dup_pkts_recv;
+
+ sprintf(srcIP, "%lu.%lu.%lu.%lu:%u",
+ ((src >> 24) & 0xFF), ((src >> 16) & 0xFF), ((src >> 8)
& 0xFF), (src
& 0xFF),
+ srcp);
+ sprintf(destIP, "%3d.%3d.%3d.%3d:%u",
+ ((dest >> 24) & 0xFF), ((dest >> 16) & 0xFF), ((dest >>
8) & 0xFF),
(dest & 0xFF),
+ destp);
+
+ seq_printf(seq, "%d: %-21s %-21s "
+ "%8lu %8lu %8lu %8lu %8lu%n",
+ num,
+ srcIP,
+ destIP,
+ SmoothedRttEstimate,
+ AcksSent,
+ DupAcksSent,
+ PktsRecv,
+ DupPktsRecv,
+
+ &len
+ );
+
+ seq_printf(seq, "%*s\n", LINESZ - 1 - len, "");
+/* ; //insert read-unlock here */
+ }
+
+out:
+ return 0;
+}
+
static const struct file_operations tcp_afinfo_seq_fops = {
.owner = THIS_MODULE,
.open = tcp_seq_open,
@@ -2541,6 +2617,15 @@
.release = seq_release_net
};
+static struct tcp_seq_afinfo tcphealth_seq_afinfo = {
+ .name = "tcphealth",
+ .family = AF_INET,
+ .seq_fops = &tcp_afinfo_seq_fops,
+ .seq_ops = {
+ .show = tcp_health_seq_show,
+ },
+};
+
static struct tcp_seq_afinfo tcp4_seq_afinfo = {
.name = "tcp",
.family = AF_INET,
@@ -2552,12 +2637,15 @@
static int __net_init tcp4_proc_init_net(struct net *net)
{
- return tcp_proc_register(net, &tcp4_seq_afinfo);
+ int ret=tcp_proc_register(net, &tcp4_seq_afinfo);
+ if(ret==0) ret=tcp_proc_register(net, &tcphealth_seq_afinfo);
+ return ret;
}
static void __net_exit tcp4_proc_exit_net(struct net *net)
{
tcp_proc_unregister(net, &tcp4_seq_afinfo);
+ tcp_proc_unregister(net, &tcphealth_seq_afinfo);
}
static struct pernet_operations tcp4_net_ops = {
diff -rub linux-3.4.4/net/ipv4/tcp_output.c
linux-3.4.4-heal-lsm/net/ipv4/tcp_output.c
--- linux-3.4.4/net/ipv4/tcp_output.c 2012-06-22 20:37:50.000000000 +0200
+++ linux-3.4.4-heal-lsm/net/ipv4/tcp_output.c 2012-07-06
17:15:14.000000000 +0200
@@ -31,6 +31,7 @@
* Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
* Cacophonix Gaul : draft-minshall-nagle-01
* J Hadi Salim : ECN support
+ * Federico D. Sacerdoti : Added TCP health monitoring.
*
*/
@@ -2754,8 +2755,15 @@
skb_reserve(buff, MAX_TCP_HEADER);
tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
+ /* If the rcv_nxt has not advanced since sending our last ACK,
this is
a duplicate. */
+ if (tcp_sk(sk)->rcv_nxt == tcp_sk(sk)->last_ack_sent)
+ tcp_sk(sk)->dup_acks_sent++;
+ /* Record the total number of acks sent on this connection. */
+ tcp_sk(sk)->acks_sent++;
+
/* Send it off, this clears delayed acks for us. */
TCP_SKB_CB(buff)->when = tcp_time_stamp;
+ tcp_sk(sk)->last_ack_sent = tcp_sk(sk)->rcv_nxt;
tcp_transmit_skb(sk, buff, 0, GFP_ATOMIC);
}
--
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