1 files changed, 39 insertions, 4 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 4028ddd14dd5..868ed74a76a8 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1889,6 +1889,22 @@ static void tcp_recv_timestamp(struct msghdr *msg, const struct sock *sk,
         }
 }
 
+static int tcp_inq_hint(struct sock *sk)
+{
+        const struct tcp_sock *tp = tcp_sk(sk);
+        u32 copied_seq = READ_ONCE(tp->copied_seq);
+        u32 rcv_nxt = READ_ONCE(tp->rcv_nxt);
+        int inq;
+
+        inq = rcv_nxt - copied_seq;
+        if (unlikely(inq < 0 || copied_seq != READ_ONCE(tp->copied_seq))) {
+                lock_sock(sk);
+                inq = tp->rcv_nxt - tp->copied_seq;
+                release_sock(sk);
+        }
+        return inq;
+}
+
 /*
  *      This routine copies from a sock struct into the user buffer.
  *
@@ -1905,13 +1921,14 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
         u32 peek_seq;
         u32 *seq;
         unsigned long used;
-        int err;
+        int err, inq;
         int target;             /* Read at least this many bytes */
         long timeo;
         struct sk_buff *skb, *last;
         u32 urg_hole = 0;
         struct scm_timestamping tss;
         bool has_tss = false;
+        bool has_cmsg;
 
         if (unlikely(flags & MSG_ERRQUEUE))
                 return inet_recv_error(sk, msg, len, addr_len);
@@ -1926,6 +1943,7 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
         if (sk->sk_state == TCP_LISTEN)
                 goto out;
 
+        has_cmsg = tp->recvmsg_inq;
         timeo = sock_rcvtimeo(sk, nonblock);
 
         /* Urgent data needs to be handled specially. */
@@ -2112,6 +2130,7 @@ skip_copy:
                 if (TCP_SKB_CB(skb)->has_rxtstamp) {
                         tcp_update_recv_tstamps(skb, &tss);
                         has_tss = true;
+                        has_cmsg = true;
                 }
                 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
                         goto found_fin_ok;
@@ -2131,13 +2150,20 @@ skip_copy:
          * on connected socket. I was just happy when found this 8) --ANK
          */
 
-        if (has_tss)
-                tcp_recv_timestamp(msg, sk, &tss);
-
         /* Clean up data we have read: This will do ACK frames. */
         tcp_cleanup_rbuf(sk, copied);
 
         release_sock(sk);
+
+        if (has_cmsg) {
+                if (has_tss)
+                        tcp_recv_timestamp(msg, sk, &tss);
+                if (tp->recvmsg_inq) {
+                        inq = tcp_inq_hint(sk);
+                        put_cmsg(msg, SOL_TCP, TCP_CM_INQ, sizeof(inq), &inq);
+                }
+        }
+
         return copied;
 
 out:
@@ -3006,6 +3032,12 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
                 tp->notsent_lowat = val;
                 sk->sk_write_space(sk);
                 break;
+        case TCP_INQ:
+                if (val > 1 || val < 0)
+                        err = -EINVAL;
+                else
+                        tp->recvmsg_inq = val;
+                break;
         default:
                 err = -ENOPROTOOPT;
                 break;
@@ -3431,6 +3463,9 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
         case TCP_NOTSENT_LOWAT:
                 val = tp->notsent_lowat;
                 break;
+        case TCP_INQ:
+                val = tp->recvmsg_inq;
+                break;
         case TCP_SAVE_SYN:
                 val = tp->save_syn;
                 break;