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Message-ID: <Pine.LNX.4.64.0810041505340.697@wrl-59.cs.helsinki.fi>
Date: Sat, 4 Oct 2008 15:08:19 +0300 (EEST)
From: "Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
To: David Miller <davem@...emloft.net>
cc: Netdev <netdev@...r.kernel.org>
Subject: [PATCHv3 net-next] tcp: kill pointless urg_mode
On Sat, 4 Oct 2008, Ilpo Järvinen wrote:
> On Fri, 3 Oct 2008, Ilpo Järvinen wrote:
>
> > On Fri, 3 Oct 2008, Ilpo Järvinen wrote:
> >
> > > It all started from me noticing that this urgent check in
> > > tcp_clean_rtx_queue is unnecessarily inside the loop. Then
> > > I took a longer look to it and found out that the users of
> > > urg_mode can trivially do without. Just drag snd_up with
> > > us when we advance.
> >
> > Please hold a minute with this one while I inspect why I saw
> > some strange urg now in a tcpdump.
>
> Ok, now it's right with win probes too...
>
> --
>
> [PATCHv2 net-next] tcp: kill pointless urg_mode
Even better this time... tcp_urg_mode moved to tcp_output.c and exchanged
the tcp_transmit_skb checks to the original order.
--
[PATCHv3 net-next] tcp: kill pointless urg_mode
It all started from me noticing that this urgent check in
tcp_clean_rtx_queue is unnecessarily inside the loop. Then
I took a longer look to it and found out that the users of
urg_mode can trivially do without, well almost, there was
one gotcha.
Bonus: those funny people who use urg with >= 2^31 write_seq -
snd_una could now rejoice too (that's the only purpose for the
between being there, otherwise a simple compare would have done
the thing). Not that I assume that the rest of the tcp code
happily lives with such mind-boggling numbers :-). Alas, it
turned out to be impossible to set wmem to such numbers anyway,
yes I really tried a big sendfile after setting some wmem but
nothing happened :-). ...Tcp_wmem is int and so is sk_sndbuf...
So I hacked a bit variable to long and found out that it seems
to work... :-)
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
---
include/linux/tcp.h | 9 ++++-----
net/ipv4/tcp.c | 4 +---
net/ipv4/tcp_input.c | 11 ++++++-----
net/ipv4/tcp_minisocks.c | 1 +
net/ipv4/tcp_output.c | 18 ++++++++++++------
5 files changed, 24 insertions(+), 19 deletions(-)
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 7672906..fe77e14 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -312,8 +312,11 @@ struct tcp_sock {
u32 retrans_out; /* Retransmitted packets out */
u16 urg_data; /* Saved octet of OOB data and control flags */
- u8 urg_mode; /* In urgent mode */
u8 ecn_flags; /* ECN status bits. */
+ u8 reordering; /* Packet reordering metric. */
+ u32 snd_up; /* Urgent pointer */
+
+ u8 keepalive_probes; /* num of allowed keep alive probes */
/*
* Options received (usually on last packet, some only on SYN packets).
*/
@@ -361,8 +364,6 @@ struct tcp_sock {
u32 lost_retrans_low; /* Sent seq after any rxmit (lowest) */
- u8 reordering; /* Packet reordering metric. */
- u8 keepalive_probes; /* num of allowed keep alive probes */
u32 prior_ssthresh; /* ssthresh saved at recovery start */
u32 high_seq; /* snd_nxt at onset of congestion */
@@ -374,8 +375,6 @@ struct tcp_sock {
u32 total_retrans; /* Total retransmits for entire connection */
u32 urg_seq; /* Seq of received urgent pointer */
- u32 snd_up; /* Urgent pointer */
-
unsigned int keepalive_time; /* time before keep alive takes place */
unsigned int keepalive_intvl; /* time interval between keep alive probes */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 1ab341e..87268d2 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -493,10 +493,8 @@ static inline void skb_entail(struct sock *sk, struct sk_buff *skb)
static inline void tcp_mark_urg(struct tcp_sock *tp, int flags,
struct sk_buff *skb)
{
- if (flags & MSG_OOB) {
- tp->urg_mode = 1;
+ if (flags & MSG_OOB)
tp->snd_up = tp->write_seq;
- }
}
static inline void tcp_push(struct sock *sk, int flags, int mss_now,
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index f1f4b12..db1f194 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2840,7 +2840,8 @@ static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
* is before the ack sequence we can discard it as it's confirmed to have
* arrived at the other end.
*/
-static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
+static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
+ u32 prior_snd_una)
{
struct tcp_sock *tp = tcp_sk(sk);
const struct inet_connection_sock *icsk = inet_csk(sk);
@@ -2907,9 +2908,6 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
if (sacked & TCPCB_LOST)
tp->lost_out -= acked_pcount;
- if (unlikely(tp->urg_mode && !before(end_seq, tp->snd_up)))
- tp->urg_mode = 0;
-
tp->packets_out -= acked_pcount;
pkts_acked += acked_pcount;
@@ -2939,6 +2937,9 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
tp->lost_skb_hint = NULL;
}
+ if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una)))
+ tp->snd_up = tp->snd_una;
+
if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
flag |= FLAG_SACK_RENEGING;
@@ -3315,7 +3316,7 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
goto no_queue;
/* See if we can take anything off of the retransmit queue. */
- flag |= tcp_clean_rtx_queue(sk, prior_fackets);
+ flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una);
if (tp->frto_counter)
frto_cwnd = tcp_process_frto(sk, flag);
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index f976fc5..779f2e9 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -395,6 +395,7 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req,
newtp->pred_flags = 0;
newtp->rcv_wup = newtp->copied_seq = newtp->rcv_nxt = treq->rcv_isn + 1;
newtp->snd_sml = newtp->snd_una = newtp->snd_nxt = treq->snt_isn + 1;
+ newtp->snd_up = treq->snt_isn + 1;
tcp_prequeue_init(newtp);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index a8499ef..f0545db 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -345,6 +345,11 @@ static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
TCP_SKB_CB(skb)->end_seq = seq;
}
+static inline int tcp_urg_mode(const struct tcp_sock *tp)
+{
+ return tp->snd_una != tp->snd_up;
+}
+
#define OPTION_SACK_ADVERTISE (1 << 0)
#define OPTION_TS (1 << 1)
#define OPTION_MD5 (1 << 2)
@@ -646,7 +651,8 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
th->check = 0;
th->urg_ptr = 0;
- if (unlikely(tp->urg_mode &&
+ /* The urg_mode check is necessary during a below snd_una win probe */
+ if (unlikely(tcp_urg_mode(tp) &&
between(tp->snd_up, tcb->seq + 1, tcb->seq + 0xFFFF))) {
th->urg_ptr = htons(tp->snd_up - tcb->seq);
th->urg = 1;
@@ -1012,7 +1018,7 @@ unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
/* Compute the current effective MSS, taking SACKs and IP options,
* and even PMTU discovery events into account.
*
- * LARGESEND note: !urg_mode is overkill, only frames up to snd_up
+ * LARGESEND note: !tcp_urg_mode is overkill, only frames up to snd_up
* cannot be large. However, taking into account rare use of URG, this
* is not a big flaw.
*/
@@ -1029,7 +1035,7 @@ unsigned int tcp_current_mss(struct sock *sk, int large_allowed)
mss_now = tp->mss_cache;
- if (large_allowed && sk_can_gso(sk) && !tp->urg_mode)
+ if (large_allowed && sk_can_gso(sk) && !tcp_urg_mode(tp))
doing_tso = 1;
if (dst) {
@@ -1193,7 +1199,7 @@ static inline int tcp_nagle_test(struct tcp_sock *tp, struct sk_buff *skb,
/* Don't use the nagle rule for urgent data (or for the final FIN).
* Nagle can be ignored during F-RTO too (see RFC4138).
*/
- if (tp->urg_mode || (tp->frto_counter == 2) ||
+ if (tcp_urg_mode(tp) || (tp->frto_counter == 2) ||
(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN))
return 1;
@@ -2358,6 +2364,7 @@ static void tcp_connect_init(struct sock *sk)
tcp_init_wl(tp, tp->write_seq, 0);
tp->snd_una = tp->write_seq;
tp->snd_sml = tp->write_seq;
+ tp->snd_up = tp->write_seq;
tp->rcv_nxt = 0;
tp->rcv_wup = 0;
tp->copied_seq = 0;
@@ -2567,8 +2574,7 @@ int tcp_write_wakeup(struct sock *sk)
tcp_event_new_data_sent(sk, skb);
return err;
} else {
- if (tp->urg_mode &&
- between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
+ if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
tcp_xmit_probe_skb(sk, 1);
return tcp_xmit_probe_skb(sk, 0);
}
--
1.5.2.2
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