first.patch

commit 16ab1b6b97313fcfc43110d5ba9f1fd37d5b3939
Author: Brendan Ashworth <brendan.ashworth@me.com>
Date:   Sat Dec 4 15:46:43 2021 -0500

    add getsockopt for last packet size

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 48d8a3633..1bbb1398e 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -412,6 +412,9 @@ struct tcp_sock {
 	 */
 	struct request_sock __rcu *fastopen_rsk;
 	struct saved_syn *saved_syn;
+
+/* TCP Nagle's algorithm optimization */
+	unsigned int opt_last_write_size;
 };
 
 enum tsq_enum {
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 8fc09e863..be298cfc9 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -129,6 +129,7 @@ enum {
 
 #define TCP_TX_DELAY		37	/* delay outgoing packets by XX usec */
 
+#define TCP_OPT_PKT_LEN     38  /* packet length of last skb sent *//
 
 #define TCP_REPAIR_ON		1
 #define TCP_REPAIR_OFF		0
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index bbb3d39c6..e63c8e153 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4155,6 +4155,9 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
 		}
 		return 0;
 	}
+	case TCP_OPT_PKT_LEN:
+		val = tp->opt_last_write_size;
+		break;
 #ifdef CONFIG_MMU
 	case TCP_ZEROCOPY_RECEIVE: {
 		struct scm_timestamping_internal tss;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 2e6e5a701..e6e9d801d 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2689,6 +2689,9 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
 		tcp_minshall_update(tp, mss_now, skb);
 		sent_pkts += tcp_skb_pcount(skb);
 
+		/* Record the sent packet size for optimization. */
+		tcp_sock->opt_last_write_size = skb->data_len;
+
 		if (push_one)
 			break;
 	}
diff --git a/tools/include/uapi/linux/tcp.h b/tools/include/uapi/linux/tcp.h
index 13ceeb395..f6f3e7bc3 100644
--- a/tools/include/uapi/linux/tcp.h
+++ b/tools/include/uapi/linux/tcp.h
@@ -129,7 +129,6 @@ enum {
 
 #define TCP_TX_DELAY		37	/* delay outgoing packets by XX usec */
 
-
 #define TCP_REPAIR_ON		1
 #define TCP_REPAIR_OFF		0
 #define TCP_REPAIR_OFF_NO_WP	-1	/* Turn off without window probes */