From 60d3915ea3b07ac0a02aaf73dbf3d99547ff33bc Mon Sep 17 00:00:00 2001
From: David Gibson <david@gibson.dropbear.id.au>
Date: Fri, 8 Sep 2023 11:49:50 +1000
Subject: [PATCH] tcp: Return consumed packet count from tcp_data_from_tap()

Currently tcp_data_from_tap() is assumed to consume all packets remaining
in the packet pool it is given.  However there are some edge cases where
that's not correct.  In preparation for fixing those, change it to return
a count of packets consumed and use that in its caller.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
 tcp.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/tcp.c b/tcp.c
index 5592998..34c27f0 100644
--- a/tcp.c
+++ b/tcp.c
@@ -2297,8 +2297,10 @@ err:
  * @idx:	Index of first data packet in pool
  *
  * #syscalls sendmsg
+ *
+ * Return: count of consumed packets
  */
-static void tcp_data_from_tap(struct ctx *c, struct tcp_tap_conn *conn,
+static int tcp_data_from_tap(struct ctx *c, struct tcp_tap_conn *conn,
 			      const struct pool *p, int idx)
 {
 	int i, iov_i, ack = 0, fin = 0, retr = 0, keep = -1, partial_send = 0;
@@ -2310,7 +2312,7 @@ static void tcp_data_from_tap(struct ctx *c, struct tcp_tap_conn *conn,
 	ssize_t n;
 
 	if (conn->events == CLOSED)
-		return;
+		return p->count - idx;
 
 	ASSERT(conn->events & ESTABLISHED);
 
@@ -2323,19 +2325,19 @@ static void tcp_data_from_tap(struct ctx *c, struct tcp_tap_conn *conn,
 		th = packet_get(p, i, 0, sizeof(*th), &len);
 		if (!th) {
 			tcp_rst(c, conn);
-			return;
+			return p->count - idx;
 		}
 		len += sizeof(*th);
 
 		off = th->doff * 4UL;
 		if (off < sizeof(*th) || off > len) {
 			tcp_rst(c, conn);
-			return;
+			return p->count - idx;
 		}
 
 		if (th->rst) {
 			conn_event(c, conn, CLOSED);
-			return;
+			return p->count - idx;
 		}
 
 		len -= off;
@@ -2446,10 +2448,10 @@ eintr:
 
 		if (errno == EAGAIN || errno == EWOULDBLOCK) {
 			tcp_send_flag(c, conn, ACK_IF_NEEDED);
-			return;
+			return p->count - idx;
 		}
 		tcp_rst(c, conn);
-		return;
+		return p->count - idx;
 	}
 
 	if (n < (int)(seq_from_tap - conn->seq_from_tap)) {
@@ -2470,7 +2472,7 @@ out:
 			conn->seq_dup_ack_approx = conn->seq_from_tap & 0xff;
 			tcp_send_flag(c, conn, DUP_ACK);
 		}
-		return;
+		return p->count - idx;
 	}
 
 	if (ack && conn->events & TAP_FIN_SENT &&
@@ -2484,6 +2486,8 @@ out:
 	} else {
 		tcp_send_flag(c, conn, ACK_IF_NEEDED);
 	}
+
+	return p->count - idx;
 }
 
 /**
@@ -2540,6 +2544,7 @@ int tcp_tap_handler(struct ctx *c, int af, const void *saddr, const void *daddr,
 	struct tcphdr *th;
 	int ack_due = 0;
 	char *opts;
+	int count;
 
 	th = packet_get(p, idx, 0, sizeof(*th), &len);
 	if (!th)
@@ -2627,7 +2632,7 @@ int tcp_tap_handler(struct ctx *c, int af, const void *saddr, const void *daddr,
 	}
 
 	/* Established connections accepting data from tap */
-	tcp_data_from_tap(c, conn, p, idx);
+	count = tcp_data_from_tap(c, conn, p, idx);
 	if (conn->seq_ack_to_tap != conn->seq_from_tap)
 		ack_due = 1;
 
@@ -2641,7 +2646,7 @@ int tcp_tap_handler(struct ctx *c, int af, const void *saddr, const void *daddr,
 	if (ack_due)
 		conn_flag(c, conn, ACK_TO_TAP_DUE);
 
-	return p->count - idx;
+	return count;
 }
 
 /**