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[PATCH] tcp: fix TSO sizing bugs
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MSS changes can be lost since we preemptively initialize the tso_segs count
for an SKB before we %100 commit to sending it out.

So, by the time we send it out, the tso_size information can be stale due
to PMTU events.  This mucks up all of the logic in our send engine, and can
even result in the BUG() triggering in tcp_tso_should_defer().

Another problem we have is that we're storing the tp->mss_cache, not the
SACK block normalized MSS, as the tso_size.  That's wrong too.

Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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David S. Miller authored and Linus Torvalds committed Aug 5, 2005
1 parent 0c3dba1 commit 846998a
Showing 1 changed file with 28 additions and 28 deletions.
56 changes: 28 additions & 28 deletions net/ipv4/tcp_output.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -403,11 +403,9 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
sk->sk_send_head = skb;
}

static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb)
static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now)
{
struct tcp_sock *tp = tcp_sk(sk);

if (skb->len <= tp->mss_cache ||
if (skb->len <= mss_now ||
!(sk->sk_route_caps & NETIF_F_TSO)) {
/* Avoid the costly divide in the normal
* non-TSO case.
Expand All @@ -417,10 +415,10 @@ static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb)
} else {
unsigned int factor;

factor = skb->len + (tp->mss_cache - 1);
factor /= tp->mss_cache;
factor = skb->len + (mss_now - 1);
factor /= mss_now;
skb_shinfo(skb)->tso_segs = factor;
skb_shinfo(skb)->tso_size = tp->mss_cache;
skb_shinfo(skb)->tso_size = mss_now;
}
}

Expand All @@ -429,7 +427,7 @@ static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb)
* packet to the list. This won't be called frequently, I hope.
* Remember, these are still headerless SKBs at this point.
*/
static int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len)
static int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, unsigned int mss_now)
{
struct tcp_sock *tp = tcp_sk(sk);
struct sk_buff *buff;
Expand Down Expand Up @@ -492,8 +490,8 @@ static int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len)
}

/* Fix up tso_factor for both original and new SKB. */
tcp_set_skb_tso_segs(sk, skb);
tcp_set_skb_tso_segs(sk, buff);
tcp_set_skb_tso_segs(sk, skb, mss_now);
tcp_set_skb_tso_segs(sk, buff, mss_now);

if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) {
tp->lost_out += tcp_skb_pcount(skb);
Expand Down Expand Up @@ -569,7 +567,7 @@ int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
* factor and mss.
*/
if (tcp_skb_pcount(skb) > 1)
tcp_set_skb_tso_segs(sk, skb);
tcp_set_skb_tso_segs(sk, skb, tcp_current_mss(sk, 1));

return 0;
}
Expand Down Expand Up @@ -734,12 +732,14 @@ static inline unsigned int tcp_cwnd_test(struct tcp_sock *tp, struct sk_buff *sk
/* This must be invoked the first time we consider transmitting
* SKB onto the wire.
*/
static inline int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb)
static inline int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now)
{
int tso_segs = tcp_skb_pcount(skb);

if (!tso_segs) {
tcp_set_skb_tso_segs(sk, skb);
if (!tso_segs ||
(tso_segs > 1 &&
skb_shinfo(skb)->tso_size != mss_now)) {
tcp_set_skb_tso_segs(sk, skb, mss_now);
tso_segs = tcp_skb_pcount(skb);
}
return tso_segs;
Expand Down Expand Up @@ -817,7 +817,7 @@ static unsigned int tcp_snd_test(struct sock *sk, struct sk_buff *skb,
struct tcp_sock *tp = tcp_sk(sk);
unsigned int cwnd_quota;

tcp_init_tso_segs(sk, skb);
tcp_init_tso_segs(sk, skb, cur_mss);

if (!tcp_nagle_test(tp, skb, cur_mss, nonagle))
return 0;
Expand Down Expand Up @@ -854,7 +854,7 @@ int tcp_may_send_now(struct sock *sk, struct tcp_sock *tp)
* know that all the data is in scatter-gather pages, and that the
* packet has never been sent out before (and thus is not cloned).
*/
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len)
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, unsigned int mss_now)
{
struct sk_buff *buff;
int nlen = skb->len - len;
Expand Down Expand Up @@ -887,8 +887,8 @@ static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len)
skb_split(skb, buff, len);

/* Fix up tso_factor for both original and new SKB. */
tcp_set_skb_tso_segs(sk, skb);
tcp_set_skb_tso_segs(sk, buff);
tcp_set_skb_tso_segs(sk, skb, mss_now);
tcp_set_skb_tso_segs(sk, buff, mss_now);

/* Link BUFF into the send queue. */
skb_header_release(buff);
Expand Down Expand Up @@ -976,7 +976,7 @@ static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle)
if (unlikely(!skb))
return 0;

tso_segs = tcp_init_tso_segs(sk, skb);
tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
cwnd_quota = tcp_cwnd_test(tp, skb);
if (unlikely(!cwnd_quota))
goto out;
Expand Down Expand Up @@ -1006,11 +1006,11 @@ static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle)
limit = skb->len - trim;
}
if (skb->len > limit) {
if (tso_fragment(sk, skb, limit))
if (tso_fragment(sk, skb, limit, mss_now))
break;
}
} else if (unlikely(skb->len > mss_now)) {
if (unlikely(tcp_fragment(sk, skb, mss_now)))
if (unlikely(tcp_fragment(sk, skb, mss_now, mss_now)))
break;
}

Expand Down Expand Up @@ -1039,7 +1039,7 @@ static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle)
skb = sk->sk_send_head;
if (!skb)
break;
tso_segs = tcp_init_tso_segs(sk, skb);
tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
}

if (likely(sent_pkts)) {
Expand Down Expand Up @@ -1076,7 +1076,7 @@ void tcp_push_one(struct sock *sk, unsigned int mss_now)

BUG_ON(!skb || skb->len < mss_now);

tso_segs = tcp_init_tso_segs(sk, skb);
tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
cwnd_quota = tcp_snd_test(sk, skb, mss_now, TCP_NAGLE_PUSH);

if (likely(cwnd_quota)) {
Expand All @@ -1093,11 +1093,11 @@ void tcp_push_one(struct sock *sk, unsigned int mss_now)
limit = skb->len - trim;
}
if (skb->len > limit) {
if (unlikely(tso_fragment(sk, skb, limit)))
if (unlikely(tso_fragment(sk, skb, limit, mss_now)))
return;
}
} else if (unlikely(skb->len > mss_now)) {
if (unlikely(tcp_fragment(sk, skb, mss_now)))
if (unlikely(tcp_fragment(sk, skb, mss_now, mss_now)))
return;
}

Expand Down Expand Up @@ -1388,7 +1388,7 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
int old_factor = tcp_skb_pcount(skb);
int new_factor;

if (tcp_fragment(sk, skb, cur_mss))
if (tcp_fragment(sk, skb, cur_mss, cur_mss))
return -ENOMEM; /* We'll try again later. */

/* New SKB created, account for it. */
Expand Down Expand Up @@ -1991,7 +1991,7 @@ int tcp_write_wakeup(struct sock *sk)
skb->len > mss) {
seg_size = min(seg_size, mss);
TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
if (tcp_fragment(sk, skb, seg_size))
if (tcp_fragment(sk, skb, seg_size, mss))
return -1;
/* SWS override triggered forced fragmentation.
* Disable TSO, the connection is too sick. */
Expand All @@ -2000,7 +2000,7 @@ int tcp_write_wakeup(struct sock *sk)
sk->sk_route_caps &= ~NETIF_F_TSO;
}
} else if (!tcp_skb_pcount(skb))
tcp_set_skb_tso_segs(sk, skb);
tcp_set_skb_tso_segs(sk, skb, mss);

TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
TCP_SKB_CB(skb)->when = tcp_time_stamp;
Expand Down

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