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tcp: Add receive timestamp support for receive zerocopy.
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tcp_recvmsg() uses the CMSG mechanism to receive control information
like packet receive timestamps. This patch adds CMSG fields to
struct tcp_zerocopy_receive, and provides receive timestamps
if available to the user.

Signed-off-by: Arjun Roy <arjunroy@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Arjun Roy authored and Jakub Kicinski committed Jan 23, 2021
1 parent 925bba2 commit 7eeba17
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Showing 2 changed files with 88 additions and 32 deletions.
4 changes: 4 additions & 0 deletions include/uapi/linux/tcp.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -354,5 +354,9 @@ struct tcp_zerocopy_receive {
__u64 copybuf_address; /* in: copybuf address (small reads) */
__s32 copybuf_len; /* in/out: copybuf bytes avail/used or error */
__u32 flags; /* in: flags */
__u64 msg_control; /* ancillary data */
__u64 msg_controllen;
__u32 msg_flags;
/* __u32 hole; Next we must add >1 u32 otherwise length checks fail. */
};
#endif /* _UAPI_LINUX_TCP_H */
116 changes: 84 additions & 32 deletions net/ipv4/tcp.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1745,6 +1745,20 @@ int tcp_set_rcvlowat(struct sock *sk, int val)
}
EXPORT_SYMBOL(tcp_set_rcvlowat);

static void tcp_update_recv_tstamps(struct sk_buff *skb,
struct scm_timestamping_internal *tss)
{
if (skb->tstamp)
tss->ts[0] = ktime_to_timespec64(skb->tstamp);
else
tss->ts[0] = (struct timespec64) {0};

if (skb_hwtstamps(skb)->hwtstamp)
tss->ts[2] = ktime_to_timespec64(skb_hwtstamps(skb)->hwtstamp);
else
tss->ts[2] = (struct timespec64) {0};
}

#ifdef CONFIG_MMU
static const struct vm_operations_struct tcp_vm_ops = {
};
Expand Down Expand Up @@ -1848,13 +1862,13 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
struct scm_timestamping_internal *tss,
int *cmsg_flags);
static int receive_fallback_to_copy(struct sock *sk,
struct tcp_zerocopy_receive *zc, int inq)
struct tcp_zerocopy_receive *zc, int inq,
struct scm_timestamping_internal *tss)
{
unsigned long copy_address = (unsigned long)zc->copybuf_address;
struct scm_timestamping_internal tss_unused;
int err, cmsg_flags_unused;
struct msghdr msg = {};
struct iovec iov;
int err;

zc->length = 0;
zc->recv_skip_hint = 0;
Expand All @@ -1868,7 +1882,7 @@ static int receive_fallback_to_copy(struct sock *sk,
return err;

err = tcp_recvmsg_locked(sk, &msg, inq, /*nonblock=*/1, /*flags=*/0,
&tss_unused, &cmsg_flags_unused);
tss, &zc->msg_flags);
if (err < 0)
return err;

Expand Down Expand Up @@ -1909,21 +1923,27 @@ static int tcp_copy_straggler_data(struct tcp_zerocopy_receive *zc,
return (__s32)copylen;
}

static int tcp_zerocopy_handle_leftover_data(struct tcp_zerocopy_receive *zc,
struct sock *sk,
struct sk_buff *skb,
u32 *seq,
s32 copybuf_len)
static int tcp_zc_handle_leftover(struct tcp_zerocopy_receive *zc,
struct sock *sk,
struct sk_buff *skb,
u32 *seq,
s32 copybuf_len,
struct scm_timestamping_internal *tss)
{
u32 offset, copylen = min_t(u32, copybuf_len, zc->recv_skip_hint);

if (!copylen)
return 0;
/* skb is null if inq < PAGE_SIZE. */
if (skb)
if (skb) {
offset = *seq - TCP_SKB_CB(skb)->seq;
else
} else {
skb = tcp_recv_skb(sk, *seq, &offset);
if (TCP_SKB_CB(skb)->has_rxtstamp) {
tcp_update_recv_tstamps(skb, tss);
zc->msg_flags |= TCP_CMSG_TS;
}
}

zc->copybuf_len = tcp_copy_straggler_data(zc, skb, copylen, &offset,
seq);
Expand Down Expand Up @@ -2010,9 +2030,37 @@ static int tcp_zerocopy_vm_insert_batch(struct vm_area_struct *vma,
err);
}

static void tcp_recv_timestamp(struct msghdr *msg, const struct sock *sk,
struct scm_timestamping_internal *tss);
static void tcp_zc_finalize_rx_tstamp(struct sock *sk,
struct tcp_zerocopy_receive *zc,
struct scm_timestamping_internal *tss)
{
unsigned long msg_control_addr;
struct msghdr cmsg_dummy;

msg_control_addr = (unsigned long)zc->msg_control;
cmsg_dummy.msg_control = (void *)msg_control_addr;
cmsg_dummy.msg_controllen =
(__kernel_size_t)zc->msg_controllen;
cmsg_dummy.msg_flags = in_compat_syscall()
? MSG_CMSG_COMPAT : 0;
zc->msg_flags = 0;
if (zc->msg_control == msg_control_addr &&
zc->msg_controllen == cmsg_dummy.msg_controllen) {
tcp_recv_timestamp(&cmsg_dummy, sk, tss);
zc->msg_control = (__u64)
((uintptr_t)cmsg_dummy.msg_control);
zc->msg_controllen =
(__u64)cmsg_dummy.msg_controllen;
zc->msg_flags = (__u32)cmsg_dummy.msg_flags;
}
}

#define TCP_ZEROCOPY_PAGE_BATCH_SIZE 32
static int tcp_zerocopy_receive(struct sock *sk,
struct tcp_zerocopy_receive *zc)
struct tcp_zerocopy_receive *zc,
struct scm_timestamping_internal *tss)
{
u32 length = 0, offset, vma_len, avail_len, copylen = 0;
unsigned long address = (unsigned long)zc->address;
Expand All @@ -2029,6 +2077,7 @@ static int tcp_zerocopy_receive(struct sock *sk,
int ret;

zc->copybuf_len = 0;
zc->msg_flags = 0;

if (address & (PAGE_SIZE - 1) || address != zc->address)
return -EINVAL;
Expand All @@ -2039,7 +2088,7 @@ static int tcp_zerocopy_receive(struct sock *sk,
sock_rps_record_flow(sk);

if (inq && inq <= copybuf_len)
return receive_fallback_to_copy(sk, zc, inq);
return receive_fallback_to_copy(sk, zc, inq, tss);

if (inq < PAGE_SIZE) {
zc->length = 0;
Expand Down Expand Up @@ -2084,6 +2133,11 @@ static int tcp_zerocopy_receive(struct sock *sk,
} else {
skb = tcp_recv_skb(sk, seq, &offset);
}

if (TCP_SKB_CB(skb)->has_rxtstamp) {
tcp_update_recv_tstamps(skb, tss);
zc->msg_flags |= TCP_CMSG_TS;
}
zc->recv_skip_hint = skb->len - offset;
frags = skb_advance_to_frag(skb, offset, &offset_frag);
if (!frags || offset_frag)
Expand Down Expand Up @@ -2126,8 +2180,7 @@ static int tcp_zerocopy_receive(struct sock *sk,
mmap_read_unlock(current->mm);
/* Try to copy straggler data. */
if (!ret)
copylen = tcp_zerocopy_handle_leftover_data(zc, sk, skb, &seq,
copybuf_len);
copylen = tcp_zc_handle_leftover(zc, sk, skb, &seq, copybuf_len, tss);

if (length + copylen) {
WRITE_ONCE(tp->copied_seq, seq);
Expand All @@ -2148,20 +2201,6 @@ static int tcp_zerocopy_receive(struct sock *sk,
}
#endif

static void tcp_update_recv_tstamps(struct sk_buff *skb,
struct scm_timestamping_internal *tss)
{
if (skb->tstamp)
tss->ts[0] = ktime_to_timespec64(skb->tstamp);
else
tss->ts[0] = (struct timespec64) {0};

if (skb_hwtstamps(skb)->hwtstamp)
tss->ts[2] = ktime_to_timespec64(skb_hwtstamps(skb)->hwtstamp);
else
tss->ts[2] = (struct timespec64) {0};
}

/* Similar to __sock_recv_timestamp, but does not require an skb */
static void tcp_recv_timestamp(struct msghdr *msg, const struct sock *sk,
struct scm_timestamping_internal *tss)
Expand Down Expand Up @@ -4105,6 +4144,7 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
}
#ifdef CONFIG_MMU
case TCP_ZEROCOPY_RECEIVE: {
struct scm_timestamping_internal tss;
struct tcp_zerocopy_receive zc = {};
int err;

Expand All @@ -4120,11 +4160,18 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
if (copy_from_user(&zc, optval, len))
return -EFAULT;
lock_sock(sk);
err = tcp_zerocopy_receive(sk, &zc);
err = tcp_zerocopy_receive(sk, &zc, &tss);
release_sock(sk);
if (len >= offsetofend(struct tcp_zerocopy_receive, err))
goto zerocopy_rcv_sk_err;
if (len >= offsetofend(struct tcp_zerocopy_receive, msg_flags))
goto zerocopy_rcv_cmsg;
switch (len) {
case offsetofend(struct tcp_zerocopy_receive, msg_flags):
goto zerocopy_rcv_cmsg;
case offsetofend(struct tcp_zerocopy_receive, msg_controllen):
case offsetofend(struct tcp_zerocopy_receive, msg_control):
case offsetofend(struct tcp_zerocopy_receive, flags):
case offsetofend(struct tcp_zerocopy_receive, copybuf_len):
case offsetofend(struct tcp_zerocopy_receive, copybuf_address):
case offsetofend(struct tcp_zerocopy_receive, err):
goto zerocopy_rcv_sk_err;
case offsetofend(struct tcp_zerocopy_receive, inq):
Expand All @@ -4133,6 +4180,11 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
default:
goto zerocopy_rcv_out;
}
zerocopy_rcv_cmsg:
if (zc.msg_flags & TCP_CMSG_TS)
tcp_zc_finalize_rx_tstamp(sk, &zc, &tss);
else
zc.msg_flags = 0;
zerocopy_rcv_sk_err:
if (!err)
zc.err = sock_error(sk);
Expand Down

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