Here is the tcp-zero-copy patch for kernel 2.6.12-6 .

From: yzy
Date: Wed Apr 05 2006 - 03:08:32 EST


Hello linux-kernel:

I do some work on tcp-zero-copy for kernel 2.6.12-6 ( vanilla ) , Here is the patch . Please review and discussion it .

The patch modify mainly these files below :
(1) include/linux/skbuff.h : add a zccd_t struct , it include the zero-copy's callback function pointer and reference count.
(2)include/net/tcp.h : add a new function tcp_sendpage_zccd( ) . It was used as send a memory page to TCP/IP stack.
(3)net/core/dev.c (4)net/core/skbuff.c : process the initial ,refcount and release of zccd information.
(5)net/ipv4/tcp.c : call the tcp_sendpage_zccd() function to send a memory page.

If have any question , Please let me know.
Thanks .
yzy@xxxxxxxxxxxxx

===============================================================================================

diff -Nur linux-2.6.12.6-orig/include/linux/skbuff.h linux-2.6.12.6/include/linux/skbuff.h
--- linux-2.6.12.6-orig/include/linux/skbuff.h 2006-03-14 19:40:26.000000000 +0800
+++ linux-2.6.12.6/include/linux/skbuff.h 2006-03-16 17:04:51.000000000 +0800
@@ -128,6 +128,30 @@
__u16 size;
};

+/* Support for callback when skb data has been released */
+typedef struct zccd /* Zero Copy Callback Descriptor */
+{ /* (embed as first member of custom struct) */
+ atomic_t zccd_count; /* reference count */
+ void (*zccd_destructor)(struct zccd *); /* callback when refcount reaches zero */
+} zccd_t;
+
+static inline void zccd_init (zccd_t *d, void (*callback)(zccd_t *))
+{
+ atomic_set (&d->zccd_count, 1);
+ d->zccd_destructor = callback;
+}
+
+static inline void zccd_get (zccd_t *d) /* take a reference */
+{
+ atomic_inc (&d->zccd_count);
+}
+
+static inline void zccd_put (zccd_t *d) /* release a reference */
+{
+ if (atomic_dec_and_test (&d->zccd_count))
+ (d->zccd_destructor)(d);
+}
+
/* This data is invariant across clones and lives at
* the end of the header data, ie. at skb->end.
*/
@@ -137,6 +161,13 @@
unsigned short tso_size;
unsigned short tso_segs;
struct sk_buff *frag_list;
+ zccd_t *zccd; /* zero copy descriptor */
+ zccd_t *zccd2; /* 2nd zero copy descriptor */
+ /* NB we expect zero-copy data to be at least 1 packet, so
+ * having 2 zccds means we don't unneccessarily split the packet
+ * where consecutive zero-copy sends abutt.
+ */
+
skb_frag_t frags[MAX_SKB_FRAGS];
};

diff -Nur linux-2.6.12.6-orig/include/net/tcp.h linux-2.6.12.6/include/net/tcp.h
--- linux-2.6.12.6-orig/include/net/tcp.h 2005-06-18 03:48:29.000000000 +0800
+++ linux-2.6.12.6/include/net/tcp.h 2006-03-16 17:05:02.000000000 +0800
@@ -783,6 +783,9 @@
extern int tcp_sendmsg(struct kiocb *iocb, struct sock *sk,
struct msghdr *msg, size_t size);
extern ssize_t tcp_sendpage(struct socket *sock, struct page *page, int offset, size_t size, int flags);
+extern ssize_t tcp_sendpage_zccd(struct socket *sock, struct page *page, int offset, size_t size,
+ int flags, zccd_t *zccd);
+

extern int tcp_ioctl(struct sock *sk, int cmd, @@ -879,6 +882,9 @@
struct msghdr *msg,
size_t len, int nonblock, int flags, int *addr_len);
+extern int tcp_recvpackets(struct sock *sk,
+ struct sk_buff_head *packets,
+ int len, int nonblock);

extern int tcp_listen_start(struct sock *sk);

diff -Nur linux-2.6.12.6-orig/net/core/dev.c linux-2.6.12.6/net/core/dev.c
--- linux-2.6.12.6-orig/net/core/dev.c 2005-06-18 03:48:29.000000000 +0800
+++ linux-2.6.12.6/net/core/dev.c 2006-03-16 17:04:36.000000000 +0800
@@ -1176,6 +1176,9 @@
ninfo->tso_segs = skb_shinfo(skb)->tso_segs;
ninfo->nr_frags = 0;
ninfo->frag_list = NULL;
+ ninfo->zccd = NULL; /* copied data => no user zero copy descriptor */
+ ninfo->zccd2 = NULL;
+

/* Offset between the two in bytes */
offset = data - skb->head;
diff -Nur linux-2.6.12.6-orig/net/core/skbuff.c linux-2.6.12.6/net/core/skbuff.c
--- linux-2.6.12.6-orig/net/core/skbuff.c 2005-06-18 03:48:29.000000000 +0800
+++ linux-2.6.12.6/net/core/skbuff.c 2006-03-16 17:04:41.000000000 +0800
@@ -159,6 +159,9 @@
skb_shinfo(skb)->tso_size = 0;
skb_shinfo(skb)->tso_segs = 0;
skb_shinfo(skb)->frag_list = NULL;
+ skb_shinfo(skb)->zccd = NULL; /* skbuffs kick off with NO user zero copy descriptors */
+ skb_shinfo(skb)->zccd2 = NULL;
+
out:
return skb;
nodata:
@@ -247,6 +250,10 @@
if (!skb->cloned ||
!atomic_sub_return(skb->nohdr ? (1 << SKB_DATAREF_SHIFT) + 1 : 1,
&skb_shinfo(skb)->dataref)) {
+ if (skb_shinfo(skb)->zccd != NULL) /* zero copy callback descriptor? */
+ zccd_put (skb_shinfo(skb)->zccd); /* release hold */
+ if (skb_shinfo(skb)->zccd2 != NULL) /* 2nd zero copy callback descriptor? */
+ zccd_put (skb_shinfo(skb)->zccd2); /* release hold */
if (skb_shinfo(skb)->nr_frags) {
int i;
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
@@ -529,6 +536,14 @@
n->data_len = skb->data_len;
n->len = skb->len;

+ if (skb_shinfo(skb)->zccd != NULL) /* user zero copy descriptor? */
+ zccd_get (skb_shinfo(skb)->zccd); /* 1 more ref (pages are shared) */
+ skb_shinfo(n)->zccd = skb_shinfo(skb)->zccd;
+
+ if (skb_shinfo(skb)->zccd2 != NULL) /* 2nd user zero copy descriptor? */
+ zccd_get (skb_shinfo(skb)->zccd2); /* 1 more ref (pages are shared) */
+ skb_shinfo(n)->zccd2 = skb_shinfo(skb)->zccd2;
+
if (skb_shinfo(skb)->nr_frags) {
int i;

@@ -571,6 +586,9 @@
u8 *data;
int size = nhead + (skb->end - skb->head) + ntail;
long off;
+ zccd_t *zccd = skb_shinfo(skb)->zccd; /* stash user zero copy descriptor */
+ zccd_t *zccd2 = skb_shinfo(skb)->zccd2; /* stash 2nd user zero copy descriptor */
+

if (skb_shared(skb))
BUG();
@@ -592,6 +610,11 @@
if (skb_shinfo(skb)->frag_list)
skb_clone_fraglist(skb);

+ if (zccd != NULL) /* user zero copy descriptor? */
+ zccd_get (zccd); /* extra ref (pages are shared) */
+ if (zccd2 != NULL) /* 2nd user zero copy descriptor? */
+ zccd_get (zccd2); /* extra ref (pages are shared) */
+
skb_release_data(skb);

off = (data + nhead) - skb->head;
@@ -606,6 +629,8 @@
skb->cloned = 0;
skb->nohdr = 0;
atomic_set(&skb_shinfo(skb)->dataref, 1);
+ skb_shinfo(skb)->zccd = zccd;
+ skb_shinfo(skb)->zccd2 = zccd2;
return 0;

nodata:
diff -Nur linux-2.6.12.6-orig/net/ipv4/tcp.c linux-2.6.12.6/net/ipv4/tcp.c
--- linux-2.6.12.6-orig/net/ipv4/tcp.c 2005-06-18 03:48:29.000000000 +0800
+++ linux-2.6.12.6/net/ipv4/tcp.c 2006-03-16 17:04:57.000000000 +0800
@@ -630,8 +630,10 @@
}
}

+/* Extra parameter: user zero copy descriptor (or NULL if not doing that) */
static ssize_t do_tcp_sendpages(struct sock *sk, struct page **pages, int poffset,
- size_t psize, int flags)
+ size_t psize, int flags, zccd_t *zccd)
+
{
struct tcp_sock *tp = tcp_sk(sk);
int mss_now;
@@ -678,6 +680,17 @@
copy = size;

i = skb_shinfo(skb)->nr_frags;
+
+ if (zccd != NULL && /* this is a zcc I/O */
+ skb_shinfo(skb)->zccd != NULL && /* skb is part of a zcc I/O */
+ skb_shinfo(skb)->zccd2 != NULL &&
+ skb_shinfo(skb)->zccd != zccd && /* not the same one */
+ skb_shinfo(skb)->zccd2 != zccd)
+ {
+ tcp_mark_push (tp, skb);
+ goto new_segment;
+ }
+
can_coalesce = skb_can_coalesce(skb, i, page, offset);
if (!can_coalesce && i >= MAX_SKB_FRAGS) {
tcp_mark_push(tp, skb);
@@ -694,6 +707,20 @@
skb_fill_page_desc(skb, i, page, offset, copy);
}

+ if (zccd != NULL && /* this is a zcc I/O */
+ skb_shinfo(skb)->zccd != zccd && /* not already referencing this zccd */
+ skb_shinfo(skb)->zccd2 != zccd)
+ {
+ zccd_get (zccd); /* bump ref count */
+
+ BUG_TRAP (skb_shinfo(skb)->zccd2 == NULL);
+
+ if (skb_shinfo(skb)->zccd == NULL) /* reference this zccd */
+ skb_shinfo(skb)->zccd = zccd;
+ else
+ skb_shinfo(skb)->zccd2 = zccd;
+ }
+
skb->len += copy;
skb->data_len += copy;
skb->truesize += copy;
@@ -762,12 +789,37 @@

lock_sock(sk);
TCP_CHECK_TIMER(sk);
- res = do_tcp_sendpages(sk, &page, offset, size, flags);
+ res = do_tcp_sendpages(sk, &page, offset, size, flags,NULL);
+ TCP_CHECK_TIMER(sk);
+ release_sock(sk);
+ return res;
+}
+
+ssize_t tcp_sendpage_zccd(struct socket *sock, struct page *page, int offset, size_t size,
+ int flags, zccd_t *zccd)
+{
+ ssize_t res;
+ struct sock *sk = sock->sk;
+
+#define TCP_ZC_CSUM_FLAGS (NETIF_F_IP_CSUM|NETIF_F_NO_CSUM|NETIF_F_HW_CSUM)
+
+ if (!(sk->sk_route_caps & NETIF_F_SG) || /* caller shouldn't waste her time */
+ !(sk->sk_route_caps & TCP_ZC_CSUM_FLAGS)) /* on double mapping */
+ BUG ();
+
+#undef TCP_ZC_CSUM_FLAGS
+
+ lock_sock(sk);
+ TCP_CHECK_TIMER(sk);
+
+ res = do_tcp_sendpages(sk, &page, offset, size, flags, zccd);
+
TCP_CHECK_TIMER(sk);
release_sock(sk);
return res;
}

+
#define TCP_PAGE(sk) (sk->sk_sndmsg_page)
#define TCP_OFF(sk) (sk->sk_sndmsg_off)

@@ -1530,6 +1582,202 @@
goto out;
}

+int tcp_recvpackets (struct sock *sk, struct sk_buff_head *packets,
+ int len, int nonblock)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ int copied;
+ long timeo;
+
+ BUG_TRAP (len > 0);
+ /*BUG_TRAP ((flags & (MSG_OOB | MSG_PEEK | MSG_TRUNC)) == 0);*/
+
+ lock_sock(sk);
+
+ TCP_CHECK_TIMER(sk);
+
+ copied = -ENOTCONN;
+ if (sk->sk_state == TCP_LISTEN)
+ goto out;
+
+ copied = 0;
+ timeo = sock_rcvtimeo(sk, nonblock);
+
+ do {
+ struct sk_buff * skb;
+ u32 offset;
+ unsigned long used;
+ int exhausted;
+ int eaten;
+
+ /* Are we at urgent data? Stop if we have read anything. */
+ if (copied && tp->urg_data && tp->urg_seq == tp->copied_seq)
+ break;
+
+ /* We need to check signals first, to get correct SIGURG
+ * handling. FIXME: Need to check this doesnt impact 1003.1g
+ * and move it down to the bottom of the loop
+ */
+ if (signal_pending(current)) {
+ if (copied)
+ break;
+ copied = timeo ? sock_intr_errno(timeo) : -EAGAIN;
+ break;
+ }
+
+ /* Next get a buffer. */
+
+ skb = skb_peek(&sk->sk_receive_queue);
+
+ if (skb == NULL) /* nothing ready */
+ {
+ if (copied) {
+ if (sk->sk_err ||
+ sk->sk_state == TCP_CLOSE ||
+ (sk->sk_shutdown & RCV_SHUTDOWN) ||
+ !timeo ||
+ (0))
+ break;
+ } else {
+ if (sock_flag(sk, SOCK_DONE))
+ break;
+
+ if (sk->sk_err) {
+ copied = sock_error(sk);
+ break;
+ }
+
+ if (sk->sk_shutdown & RCV_SHUTDOWN)
+ break;
+
+ if (sk->sk_state == TCP_CLOSE) {
+ if (!(sock_flag(sk, SOCK_DONE))) {
+ /* This occurs when user tries to read
+ * from never connected socket.
+ */
+ copied = -ENOTCONN;
+ break;
+ }
+ break;
+ }
+
+ if (!timeo) {
+ copied = -EAGAIN;
+ break;
+ }
+ }
+
+ cleanup_rbuf(sk, copied);
+ sk_wait_data(sk, &timeo);
+ continue;
+ }
+
+ BUG_TRAP (atomic_read (&skb->users) == 1);
+
+ exhausted = eaten = 0;
+
+ offset = tp->copied_seq - TCP_SKB_CB(skb)->seq;
+ if (skb->h.th->syn)
+ offset--;
+
+ used = skb->len - offset;
+
+ if (tp->urg_data) {
+ u32 urg_offset = tp->urg_seq - tp->copied_seq;
+ if (urg_offset < used) {
+ if (!urg_offset) { /* at urgent date */
+ if (!(sock_flag(sk, SOCK_URGINLINE))) {
+ tp->copied_seq++; /* discard the single byte of urgent data */
+ offset++;
+ used--;
+ }
+ } else /* truncate read */
+ used = urg_offset;
+ }
+ }
+
+ BUG_TRAP (used >= 0);
+ if (len < used)
+ used = len;
+
+ if (used == 0)
+ exhausted = 1;
+ else
+ {
+ if (skb_is_nonlinear (skb))
+ {
+ int rc = skb_linearize (skb, GFP_KERNEL);
+
+ printk ("tcp_recvpackets(): linearising: %d\n", rc);
+
+ if (rc)
+ {
+ if (!copied)
+ copied = rc;
+ break;
+ }
+ }
+
+ if ((offset + used) == skb->len) /* consuming the whole packet */
+ {
+ __skb_unlink (skb, &sk->sk_receive_queue);
+ dst_release (skb->dst);
+ skb_orphan (skb);
+ __skb_pull (skb, offset);
+ __skb_queue_tail (packets, skb);
+ exhausted = eaten = 1;
+ }
+ else /* consuming only part of the packet */
+ {
+ struct sk_buff *skb2 = skb_clone (skb, GFP_KERNEL);
+
+ if (skb2 == NULL)
+ {
+ if (!copied)
+ copied = -ENOMEM;
+ break;
+ }
+
+ dst_release (skb2->dst);
+ __skb_pull (skb2, offset);
+ __skb_trim (skb2, used);
+ __skb_queue_tail (packets, skb2);
+ }
+
+ tp->copied_seq += used;
+ copied += used;
+ len -= used;
+ }
+
+ if (tp->urg_data && after(tp->copied_seq,tp->urg_seq)) {
+ tp->urg_data = 0;
+ tcp_fast_path_check(sk, tp);
+ }
+
+ if (!exhausted)
+ continue;
+
+ if (skb->h.th->fin)
+ {
+ tp->copied_seq++;
+ if (!eaten)
+ sk_eat_skb (sk, skb);
+ break;
+ }
+
+ if (!eaten)
+ sk_eat_skb (sk, skb);
+
+ } while (len > 0);
+
+ out:
+ /* Clean up data we have read: This will do ACK frames. */
+ cleanup_rbuf(sk, copied);
+ TCP_CHECK_TIMER(sk);
+ release_sock(sk);
+ return copied;
+}
+
/*
* State processing on a close. This implements the state shift for
* sending our FIN frame. Note that we only send a FIN for some
@@ -2380,6 +2628,8 @@
EXPORT_SYMBOL(tcp_recvmsg);
EXPORT_SYMBOL(tcp_sendmsg);
EXPORT_SYMBOL(tcp_sendpage);
+EXPORT_SYMBOL(tcp_sendpage_zccd);
+EXPORT_SYMBOL(tcp_recvpackets);
EXPORT_SYMBOL(tcp_setsockopt);
EXPORT_SYMBOL(tcp_shutdown);
EXPORT_SYMBOL(tcp_statistics);


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