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SubjectRe: 2.6.24-rc8-mm1 : net tcp_input.c warnings
On Wed, 23 Jan 2008, Dave Young wrote:

> On Jan 23, 2008 3:41 PM, Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> wrote:
> >
> > On Tue, 22 Jan 2008, David Miller wrote:
> >
> > > From: "Dave Young" <hidave.darkstar@gmail.com>
> > > Date: Wed, 23 Jan 2008 09:44:30 +0800
> > >
> > > > On Jan 22, 2008 6:47 PM, Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> wrote:
> > > > > [PATCH] [TCP]: debug S+L
> > > >
> > > > Thanks, If there's new findings I will let you know.
> > >
> > > Thanks for helping with this bug Dave.
> >
> > I noticed btw that there thing might (is likely to) spuriously trigger at
> > WARN_ON(sacked != tp->sacked_out); because those won't be equal when SACK
> > is not enabled. If that does happen too often, I send a fixed patch for
> > it, yet, the fact that I print print tp->rx_opt.sack_ok allows
> > identification of those cases already as it's zero when SACK is not
> > enabled.
> >
> > Just ask if you need the updated debug patch.
>
> Thanks, please send, I would like to get it.

There you go. I fixed non-SACK case by adding tcp_is_sack checks there and
also added two verifys to tcp_ack to see if there's corruption outside of
TCP.

--
i.

[PATCH] [TCP]: debug S+L

---
include/net/tcp.h | 8 +++-
net/ipv4/tcp_input.c | 10 +++++
net/ipv4/tcp_ipv4.c | 101 +++++++++++++++++++++++++++++++++++++++++++++++++
net/ipv4/tcp_output.c | 21 +++++++---
4 files changed, 133 insertions(+), 7 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 7de4ea3..0685035 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -272,6 +272,8 @@ DECLARE_SNMP_STAT(struct tcp_mib, tcp_statistics);
#define TCP_ADD_STATS_BH(field, val) SNMP_ADD_STATS_BH(tcp_statistics, field, val)
#define TCP_ADD_STATS_USER(field, val) SNMP_ADD_STATS_USER(tcp_statistics, field, val)

+extern void tcp_verify_wq(struct sock *sk);
+
extern void tcp_v4_err(struct sk_buff *skb, u32);

extern void tcp_shutdown (struct sock *sk, int how);
@@ -768,7 +770,11 @@ static inline __u32 tcp_current_ssthresh(const struct sock *sk)
}

/* Use define here intentionally to get WARN_ON location shown at the caller */
-#define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
+#define tcp_verify_left_out(tp) \
+ do { \
+ WARN_ON(tcp_left_out(tp) > tp->packets_out); \
+ tcp_verify_wq((struct sock *)tp); \
+ } while(0)

extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
extern __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index fa2c85c..cdacf70 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2645,6 +2645,10 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
if (do_lost || (tcp_is_fack(tp) && tcp_head_timedout(sk)))
tcp_update_scoreboard(sk, fast_rexmit);
tcp_cwnd_down(sk, flag);
+
+ WARN_ON(tcp_write_queue_head(sk) == NULL);
+ WARN_ON(!tp->packets_out);
+
tcp_xmit_retransmit_queue(sk);
}

@@ -2848,6 +2852,8 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
tcp_clear_all_retrans_hints(tp);
}

+ tcp_verify_left_out(tp);
+
if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
flag |= FLAG_SACK_RENEGING;

@@ -3175,6 +3181,8 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
prior_fackets = tp->fackets_out;
prior_in_flight = tcp_packets_in_flight(tp);

+ tcp_verify_left_out(tp);
+
if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
/* Window is constant, pure forward advance.
* No more checks are required.
@@ -3237,6 +3245,8 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP))
dst_confirm(sk->sk_dst_cache);

+ tcp_verify_left_out(tp);
+
return 1;

no_queue:
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 9aea88b..7e8ab40 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -108,6 +108,107 @@ struct inet_hashinfo __cacheline_aligned tcp_hashinfo = {
.lhash_wait = __WAIT_QUEUE_HEAD_INITIALIZER(tcp_hashinfo.lhash_wait),
};

+void tcp_print_queue(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb;
+ char s[50+1];
+ char h[50+1];
+ int idx = 0;
+ int i;
+
+ tcp_for_write_queue(skb, sk) {
+ if (skb == tcp_send_head(sk))
+ break;
+
+ for (i = 0; i < tcp_skb_pcount(skb); i++) {
+ if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) {
+ s[idx] = 'S';
+ if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
+ s[idx] = 'B';
+
+ } else if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) {
+ s[idx] = 'L';
+ } else {
+ s[idx] = ' ';
+ }
+ if (s[idx] != ' ' && skb->len < tp->mss_cache)
+ s[idx] += 'a' - 'A';
+
+ if (i == 0) {
+ if (TCP_SKB_CB(skb)->seq == tcp_highest_sack_seq(tp))
+ h[idx] = 'h';
+ else
+ h[idx] = '+';
+ } else {
+ h[idx] = '-';
+ }
+
+ if (++idx >= 50) {
+ s[idx] = 0;
+ h[idx] = 0;
+ printk(KERN_ERR "TCP wq(s) %s\n", s);
+ printk(KERN_ERR "TCP wq(h) %s\n", h);
+ idx = 0;
+ }
+ }
+ }
+ if (idx) {
+ s[idx] = '<';
+ s[idx+1] = 0;
+ h[idx] = '<';
+ h[idx+1] = 0;
+ printk(KERN_ERR "TCP wq(s) %s\n", s);
+ printk(KERN_ERR "TCP wq(h) %s\n", h);
+ }
+ printk(KERN_ERR "l%u s%u f%u p%u seq: su%u hs%u sn%u\n",
+ tp->lost_out, tp->sacked_out, tp->fackets_out, tp->packets_out,
+ tp->snd_una, tcp_highest_sack_seq(tp), tp->snd_nxt);
+}
+
+void tcp_verify_wq(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ u32 lost = 0;
+ u32 sacked = 0;
+ u32 packets = 0;
+ struct sk_buff *skb;
+
+ tcp_for_write_queue(skb, sk) {
+ if (skb == tcp_send_head(sk))
+ break;
+
+ if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) {
+ sacked += tcp_skb_pcount(skb);
+ if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
+ printk(KERN_ERR "Sacked bitmap S+L: %u %u-%u/%u\n",
+ TCP_SKB_CB(skb)->sacked,
+ TCP_SKB_CB(skb)->end_seq - tp->snd_una,
+ TCP_SKB_CB(skb)->seq - tp->snd_una,
+ tp->snd_una);
+ }
+ if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
+ lost += tcp_skb_pcount(skb);
+
+ packets += tcp_skb_pcount(skb);
+ }
+
+ WARN_ON(lost != tp->lost_out);
+ WARN_ON(tcp_is_sack(tp) && (sacked != tp->sacked_out));
+ WARN_ON(packets != tp->packets_out);
+ if ((lost != tp->lost_out) ||
+ (tcp_is_sack(tp) && (sacked != tp->sacked_out)) ||
+ (packets != tp->packets_out)) {
+ printk(KERN_ERR "P: %u L: %u vs %u S: %u vs %u w: %u-%u (%u)\n",
+ tp->packets_out,
+ lost, tp->lost_out,
+ sacked, tp->sacked_out,
+ tp->snd_una, tp->snd_nxt,
+ tp->rx_opt.sack_ok);
+ tcp_print_queue(sk);
+ }
+}
+
static int tcp_v4_get_port(struct sock *sk, unsigned short snum)
{
return inet_csk_get_port(&tcp_hashinfo, sk, snum,
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 89f0188..648340f 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -779,10 +779,9 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
tp->lost_out -= diff;

/* Adjust Reno SACK estimate. */
- if (tcp_is_reno(tp) && diff > 0) {
+ if (tcp_is_reno(tp) && diff > 0)
tcp_dec_pcount_approx_int(&tp->sacked_out, diff);
- tcp_verify_left_out(tp);
- }
+
tcp_adjust_fackets_out(sk, skb, diff);
}

@@ -790,6 +789,8 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
skb_header_release(buff);
tcp_insert_write_queue_after(skb, buff, sk);

+ tcp_verify_left_out(tp);
+
return 0;
}

@@ -1463,6 +1464,7 @@ static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle)
} else if (result > 0) {
sent_pkts = 1;
}
+ tcp_verify_left_out(tp);

while ((skb = tcp_send_head(sk))) {
unsigned int limit;
@@ -1764,6 +1766,7 @@ static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb,
tcp_clear_retrans_hints_partial(tp);

sk_wmem_free_skb(sk, next_skb);
+ tcp_verify_left_out(tp);
}

/* Do a simple retransmit without using the backoff mechanisms in
@@ -1795,13 +1798,13 @@ void tcp_simple_retransmit(struct sock *sk)
}
}

+ tcp_verify_left_out(tp);
+
tcp_clear_all_retrans_hints(tp);

if (!lost)
return;

- tcp_verify_left_out(tp);
-
/* Don't muck with the congestion window here.
* Reason is that we do not increase amount of _data_
* in network, but units changed and effective
@@ -1970,8 +1973,10 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
* packet to be MSS sized and all the
* packet counting works out.
*/
- if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
+ if (tcp_packets_in_flight(tp) >= tp->snd_cwnd) {
+ tcp_verify_left_out(tp);
return;
+ }

if (sacked & TCPCB_LOST) {
if (!(sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))) {
@@ -1997,6 +2002,8 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
}
}

+ tcp_verify_left_out(tp);
+
/* OK, demanded retransmission is finished. */

/* Forward retransmissions are possible only during Recovery. */
@@ -2054,6 +2061,8 @@ void tcp_xmit_retransmit_queue(struct sock *sk)

NET_INC_STATS_BH(LINUX_MIB_TCPFORWARDRETRANS);
}
+
+ tcp_verify_left_out(tp);
}

/* Send a fin. The caller locks the socket for us. This cannot be
--
1.5.2.2
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