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tcp: add TTL to SCM_TIMESTAMPING_OPT_STATS
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This patch adds TCP_NLA_TTL to SCM_TIMESTAMPING_OPT_STATS that exports
the time-to-live or hop limit of the latest incoming packet with
SCM_TSTAMP_ACK. The value exported may not be from the packet that acks
the sequence when incoming packets are aggregated. Exporting the
time-to-live or hop limit value of incoming packets helps to estimate
the hop count of the path of the flow that may change over time.

Signed-off-by: Yousuk Seung <ysseung@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Link: https://lore.kernel.org/r/20210120204155.552275-1-ysseung@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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@yousukseung @kuba-moo
yousukseung authored and kuba-moo committed Jan 23, 2021
1 parent a05a728 commit e7ed11e
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Showing 7 changed files with 34 additions and 14 deletions.
2 changes: 1 addition & 1 deletion include/linux/skbuff.h
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Original file line number Diff line number Diff line change
Expand Up @@ -3859,7 +3859,7 @@ static inline bool skb_defer_rx_timestamp(struct sk_buff *skb)
void skb_complete_tx_timestamp(struct sk_buff *skb,
struct skb_shared_hwtstamps *hwtstamps);

void __skb_tstamp_tx(struct sk_buff *orig_skb,
void __skb_tstamp_tx(struct sk_buff *orig_skb, const struct sk_buff *ack_skb,
struct skb_shared_hwtstamps *hwtstamps,
struct sock *sk, int tstype);

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3 changes: 2 additions & 1 deletion include/linux/tcp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -496,7 +496,8 @@ static inline u32 tcp_saved_syn_len(const struct saved_syn *saved_syn)
}

struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk,
const struct sk_buff *orig_skb);
const struct sk_buff *orig_skb,
const struct sk_buff *ack_skb);

static inline u16 tcp_mss_clamp(const struct tcp_sock *tp, u16 mss)
{
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1 change: 1 addition & 0 deletions include/uapi/linux/tcp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -314,6 +314,7 @@ enum {
TCP_NLA_TIMEOUT_REHASH, /* Timeout-triggered rehash attempts */
TCP_NLA_BYTES_NOTSENT, /* Bytes in write queue not yet sent */
TCP_NLA_EDT, /* Earliest departure time (CLOCK_MONOTONIC) */
TCP_NLA_TTL, /* TTL or hop limit of a packet received */
};

/* for TCP_MD5SIG socket option */
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2 changes: 1 addition & 1 deletion net/core/dev.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4084,7 +4084,7 @@ static int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
skb_reset_mac_header(skb);

if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_SCHED_TSTAMP))
__skb_tstamp_tx(skb, NULL, skb->sk, SCM_TSTAMP_SCHED);
__skb_tstamp_tx(skb, NULL, NULL, skb->sk, SCM_TSTAMP_SCHED);

/* Disable soft irqs for various locks below. Also
* stops preemption for RCU.
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6 changes: 4 additions & 2 deletions net/core/skbuff.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4721,6 +4721,7 @@ void skb_complete_tx_timestamp(struct sk_buff *skb,
EXPORT_SYMBOL_GPL(skb_complete_tx_timestamp);

void __skb_tstamp_tx(struct sk_buff *orig_skb,
const struct sk_buff *ack_skb,
struct skb_shared_hwtstamps *hwtstamps,
struct sock *sk, int tstype)
{
Expand All @@ -4743,7 +4744,8 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
if ((sk->sk_tsflags & SOF_TIMESTAMPING_OPT_STATS) &&
sk->sk_protocol == IPPROTO_TCP &&
sk->sk_type == SOCK_STREAM) {
skb = tcp_get_timestamping_opt_stats(sk, orig_skb);
skb = tcp_get_timestamping_opt_stats(sk, orig_skb,
ack_skb);
opt_stats = true;
} else
#endif
Expand Down Expand Up @@ -4772,7 +4774,7 @@ EXPORT_SYMBOL_GPL(__skb_tstamp_tx);
void skb_tstamp_tx(struct sk_buff *orig_skb,
struct skb_shared_hwtstamps *hwtstamps)
{
return __skb_tstamp_tx(orig_skb, hwtstamps, orig_skb->sk,
return __skb_tstamp_tx(orig_skb, NULL, hwtstamps, orig_skb->sk,
SCM_TSTAMP_SND);
}
EXPORT_SYMBOL_GPL(skb_tstamp_tx);
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18 changes: 17 additions & 1 deletion net/ipv4/tcp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3767,11 +3767,24 @@ static size_t tcp_opt_stats_get_size(void)
nla_total_size(sizeof(u16)) + /* TCP_NLA_TIMEOUT_REHASH */
nla_total_size(sizeof(u32)) + /* TCP_NLA_BYTES_NOTSENT */
nla_total_size_64bit(sizeof(u64)) + /* TCP_NLA_EDT */
nla_total_size(sizeof(u8)) + /* TCP_NLA_TTL */
0;
}

/* Returns TTL or hop limit of an incoming packet from skb. */
static u8 tcp_skb_ttl_or_hop_limit(const struct sk_buff *skb)
{
if (skb->protocol == htons(ETH_P_IP))
return ip_hdr(skb)->ttl;
else if (skb->protocol == htons(ETH_P_IPV6))
return ipv6_hdr(skb)->hop_limit;
else
return 0;
}

struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk,
const struct sk_buff *orig_skb)
const struct sk_buff *orig_skb,
const struct sk_buff *ack_skb)
{
const struct tcp_sock *tp = tcp_sk(sk);
struct sk_buff *stats;
Expand Down Expand Up @@ -3827,6 +3840,9 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk,
max_t(int, 0, tp->write_seq - tp->snd_nxt));
nla_put_u64_64bit(stats, TCP_NLA_EDT, orig_skb->skb_mstamp_ns,
TCP_NLA_PAD);
if (ack_skb)
nla_put_u8(stats, TCP_NLA_TTL,
tcp_skb_ttl_or_hop_limit(ack_skb));

return stats;
}
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16 changes: 8 additions & 8 deletions net/ipv4/tcp_input.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3145,7 +3145,7 @@ static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
}

static void tcp_ack_tstamp(struct sock *sk, struct sk_buff *skb,
u32 prior_snd_una)
const struct sk_buff *ack_skb, u32 prior_snd_una)
{
const struct skb_shared_info *shinfo;

Expand All @@ -3157,7 +3157,7 @@ static void tcp_ack_tstamp(struct sock *sk, struct sk_buff *skb,
if (!before(shinfo->tskey, prior_snd_una) &&
before(shinfo->tskey, tcp_sk(sk)->snd_una)) {
tcp_skb_tsorted_save(skb) {
__skb_tstamp_tx(skb, NULL, sk, SCM_TSTAMP_ACK);
__skb_tstamp_tx(skb, ack_skb, NULL, sk, SCM_TSTAMP_ACK);
} tcp_skb_tsorted_restore(skb);
}
}
Expand All @@ -3166,8 +3166,8 @@ static void tcp_ack_tstamp(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, u32 prior_fack,
u32 prior_snd_una,
static int tcp_clean_rtx_queue(struct sock *sk, const struct sk_buff *ack_skb,
u32 prior_fack, u32 prior_snd_una,
struct tcp_sacktag_state *sack, bool ece_ack)
{
const struct inet_connection_sock *icsk = inet_csk(sk);
Expand Down Expand Up @@ -3256,7 +3256,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, u32 prior_fack,
if (!fully_acked)
break;

tcp_ack_tstamp(sk, skb, prior_snd_una);
tcp_ack_tstamp(sk, skb, ack_skb, prior_snd_una);

next = skb_rb_next(skb);
if (unlikely(skb == tp->retransmit_skb_hint))
Expand All @@ -3274,7 +3274,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, u32 prior_fack,
tp->snd_up = tp->snd_una;

if (skb) {
tcp_ack_tstamp(sk, skb, prior_snd_una);
tcp_ack_tstamp(sk, skb, ack_skb, prior_snd_una);
if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
flag |= FLAG_SACK_RENEGING;
}
Expand Down Expand Up @@ -3809,8 +3809,8 @@ static int tcp_ack(struct sock *sk, const 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_fack, prior_snd_una, &sack_state,
flag & FLAG_ECE);
flag |= tcp_clean_rtx_queue(sk, skb, prior_fack, prior_snd_una,
&sack_state, flag & FLAG_ECE);

tcp_rack_update_reo_wnd(sk, &rs);

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