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tcp: factor out tcp_build_frag()
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Will be needed by the next patch, as MPTCP needs to handle
directly the error/memory-allocation-needed path.

No functional changes intended.

Additionally let MPTCP code access the tcp_remove_empty_skb()
helper.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Paolo Abeni authored and Jakub Kicinski committed Nov 16, 2020
1 parent c0a645a commit b796d04
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Showing 2 changed files with 70 additions and 52 deletions.
3 changes: 3 additions & 0 deletions include/net/tcp.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -322,13 +322,16 @@ void tcp_shutdown(struct sock *sk, int how);
int tcp_v4_early_demux(struct sk_buff *skb);
int tcp_v4_rcv(struct sk_buff *skb);

void tcp_remove_empty_skb(struct sock *sk, struct sk_buff *skb);
int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size);
int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
int flags);
int tcp_sendpage_locked(struct sock *sk, struct page *page, int offset,
size_t size, int flags);
struct sk_buff *tcp_build_frag(struct sock *sk, int size_goal, int flags,
struct page *page, int offset, size_t *size);
ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
size_t size, int flags);
int tcp_send_mss(struct sock *sk, int *size_goal, int flags);
Expand Down
119 changes: 67 additions & 52 deletions net/ipv4/tcp.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -954,7 +954,7 @@ int tcp_send_mss(struct sock *sk, int *size_goal, int flags)
* importantly be able to generate EPOLLOUT for Edge Trigger epoll()
* users.
*/
static void tcp_remove_empty_skb(struct sock *sk, struct sk_buff *skb)
void tcp_remove_empty_skb(struct sock *sk, struct sk_buff *skb)
{
if (skb && !skb->len) {
tcp_unlink_write_queue(skb, sk);
Expand All @@ -964,6 +964,68 @@ static void tcp_remove_empty_skb(struct sock *sk, struct sk_buff *skb)
}
}

struct sk_buff *tcp_build_frag(struct sock *sk, int size_goal, int flags,
struct page *page, int offset, size_t *size)
{
struct sk_buff *skb = tcp_write_queue_tail(sk);
struct tcp_sock *tp = tcp_sk(sk);
bool can_coalesce;
int copy, i;

if (!skb || (copy = size_goal - skb->len) <= 0 ||
!tcp_skb_can_collapse_to(skb)) {
new_segment:
if (!sk_stream_memory_free(sk))
return NULL;

skb = sk_stream_alloc_skb(sk, 0, sk->sk_allocation,
tcp_rtx_and_write_queues_empty(sk));
if (!skb)
return NULL;

#ifdef CONFIG_TLS_DEVICE
skb->decrypted = !!(flags & MSG_SENDPAGE_DECRYPTED);
#endif
skb_entail(sk, skb);
copy = size_goal;
}

if (copy > *size)
copy = *size;

i = skb_shinfo(skb)->nr_frags;
can_coalesce = skb_can_coalesce(skb, i, page, offset);
if (!can_coalesce && i >= sysctl_max_skb_frags) {
tcp_mark_push(tp, skb);
goto new_segment;
}
if (!sk_wmem_schedule(sk, copy))
return NULL;

if (can_coalesce) {
skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
} else {
get_page(page);
skb_fill_page_desc(skb, i, page, offset, copy);
}

if (!(flags & MSG_NO_SHARED_FRAGS))
skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;

skb->len += copy;
skb->data_len += copy;
skb->truesize += copy;
sk_wmem_queued_add(sk, copy);
sk_mem_charge(sk, copy);
skb->ip_summed = CHECKSUM_PARTIAL;
WRITE_ONCE(tp->write_seq, tp->write_seq + copy);
TCP_SKB_CB(skb)->end_seq += copy;
tcp_skb_pcount_set(skb, 0);

*size = copy;
return skb;
}

ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
size_t size, int flags)
{
Expand Down Expand Up @@ -999,60 +1061,13 @@ ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
goto out_err;

while (size > 0) {
struct sk_buff *skb = tcp_write_queue_tail(sk);
int copy, i;
bool can_coalesce;

if (!skb || (copy = size_goal - skb->len) <= 0 ||
!tcp_skb_can_collapse_to(skb)) {
new_segment:
if (!sk_stream_memory_free(sk))
goto wait_for_space;

skb = sk_stream_alloc_skb(sk, 0, sk->sk_allocation,
tcp_rtx_and_write_queues_empty(sk));
if (!skb)
goto wait_for_space;

#ifdef CONFIG_TLS_DEVICE
skb->decrypted = !!(flags & MSG_SENDPAGE_DECRYPTED);
#endif
skb_entail(sk, skb);
copy = size_goal;
}
struct sk_buff *skb;
size_t copy = size;

if (copy > size)
copy = size;

i = skb_shinfo(skb)->nr_frags;
can_coalesce = skb_can_coalesce(skb, i, page, offset);
if (!can_coalesce && i >= sysctl_max_skb_frags) {
tcp_mark_push(tp, skb);
goto new_segment;
}
if (!sk_wmem_schedule(sk, copy))
skb = tcp_build_frag(sk, size_goal, flags, page, offset, &copy);
if (!skb)
goto wait_for_space;

if (can_coalesce) {
skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
} else {
get_page(page);
skb_fill_page_desc(skb, i, page, offset, copy);
}

if (!(flags & MSG_NO_SHARED_FRAGS))
skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;

skb->len += copy;
skb->data_len += copy;
skb->truesize += copy;
sk_wmem_queued_add(sk, copy);
sk_mem_charge(sk, copy);
skb->ip_summed = CHECKSUM_PARTIAL;
WRITE_ONCE(tp->write_seq, tp->write_seq + copy);
TCP_SKB_CB(skb)->end_seq += copy;
tcp_skb_pcount_set(skb, 0);

if (!copied)
TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_PSH;

Expand Down

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