[PATCH v4 0/2] tcp: unify IPv4 and IPv6 tap queues

[PATCH v4 0/2] tcp: unify IPv4 and IPv6 tap queues

[Jon Maloy]

This should save us some memory and code.

---
v2: - Setting pointers to pre-set IP and MAC headers on the fly
      instead of copying them.
    - Merged patch #2 and #3 from v1
v3: - Changes based on feedback from team
v4: - Rebased to latest version of master branch

Jon Maloy (2):
  tcp: set ip and eth headers in l2 tap queues on the fly
  tcp: unify l2 TCPv4 and TCPv6 queues and structures

 tcp.c     |   6 +-
 tcp_buf.c | 272 ++++++++++++++++++------------------------------------
 tcp_buf.h |   3 +-
 3 files changed, 91 insertions(+), 190 deletions(-)

-- 
2.45.2

[PATCH v4 1/2] tcp: set ip and eth headers in l2 tap queues on the fly

[Jon Maloy]

l2 tap queue entries are currently initialized at system start, and
reused with preset headers through its whole life time. The only
fields we need to update per message are things like payload size
and checksums.

If we want to reuse these entries between ipv4 and ipv6 messages we
will need to set the pointer to the right header on the fly per
message, since the header type may differ between entries in the same
queue.

The same needs to be done for the ethernet header.

We do these changes here.

Signed-off-by: Jon Maloy <jmaloy@redhat.com>

---
v2: Setting pointers to pre-initialized IP and MAC headers instead of
    copying them in on the fly.
v3: Adapted to D. Gibson's recent commit eliminitaing overlapping memcpy()
---
 tcp_buf.c | 54 ++++++++++++++++++++++++++++++------------------------
 1 file changed, 30 insertions(+), 24 deletions(-)

diff --git a/tcp_buf.c b/tcp_buf.c
index 238827b..e4fa59f 100644
--- a/tcp_buf.c
+++ b/tcp_buf.c
@@ -130,8 +130,7 @@ void tcp_sock4_iov_init(const struct ctx *c)
 		iov = tcp4_l2_iov[i];
 
 		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp4_payload_tap_hdr[i]);
-		iov[TCP_IOV_ETH] = IOV_OF_LVALUE(tcp4_eth_src);
-		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_payload_ip[i]);
+		iov[TCP_IOV_ETH].iov_len = sizeof(struct ethhdr);
 		iov[TCP_IOV_PAYLOAD].iov_base = &tcp4_payload[i];
 	}
 
@@ -173,8 +172,7 @@ void tcp_sock6_iov_init(const struct ctx *c)
 		iov = tcp6_l2_iov[i];
 
 		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp6_payload_tap_hdr[i]);
-		iov[TCP_IOV_ETH] = IOV_OF_LVALUE(tcp6_eth_src);
-		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_payload_ip[i]);
+		iov[TCP_IOV_ETH].iov_len = sizeof(struct ethhdr);
 		iov[TCP_IOV_PAYLOAD].iov_base = &tcp6_payload[i];
 	}
 
@@ -273,11 +271,17 @@ int tcp_buf_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
 	uint32_t seq;
 	int ret;
 
-	if (CONN_V4(conn))
-		iov = tcp4_l2_flags_iov[tcp4_flags_used++];
-	else
-		iov = tcp6_l2_flags_iov[tcp6_flags_used++];
-
+	if (CONN_V4(conn)) {
+		iov = tcp4_l2_flags_iov[tcp4_flags_used];
+		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_flags_ip[tcp4_flags_used]);
+		iov[TCP_IOV_ETH].iov_base = &tcp4_eth_src;
+		tcp4_flags_used++;
+	} else {
+		iov = tcp6_l2_flags_iov[tcp6_flags_used];
+		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_flags_ip[tcp6_flags_used]);
+		iov[TCP_IOV_ETH].iov_base = &tcp6_eth_src;
+		tcp6_flags_used++;
+	}
 	payload = iov[TCP_IOV_PAYLOAD].iov_base;
 
 	seq = conn->seq_to_tap;
@@ -296,21 +300,19 @@ int tcp_buf_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
 
 	if (flags & DUP_ACK) {
 		struct iovec *dup_iov;
-		int i;
 
 		if (CONN_V4(conn))
 			dup_iov = tcp4_l2_flags_iov[tcp4_flags_used++];
 		else
-			dup_iov = tcp6_l2_flags_iov[tcp6_flags_used++];
-
-		for (i = 0; i < TCP_NUM_IOVS; i++) {
-			/* All frames share the same ethernet header buffer */
-			if (i != TCP_IOV_ETH) {
-				memcpy(dup_iov[i].iov_base, iov[i].iov_base,
-				       iov[i].iov_len);
-			}
-		}
-		dup_iov[TCP_IOV_PAYLOAD].iov_len = iov[TCP_IOV_PAYLOAD].iov_len;
+			dup_iov = tcp4_l2_flags_iov[tcp6_flags_used++];
+
+		memcpy(dup_iov[TCP_IOV_TAP].iov_base, iov[TCP_IOV_TAP].iov_base,
+		       iov[TCP_IOV_TAP].iov_len);
+		dup_iov[TCP_IOV_ETH].iov_base = iov[TCP_IOV_ETH].iov_base;
+		dup_iov[TCP_IOV_IP] = IOV_OF_LVALUE(iov[TCP_IOV_IP]);
+		memcpy(dup_iov[TCP_IOV_PAYLOAD].iov_base,
+		       iov[TCP_IOV_PAYLOAD].iov_base, l4len);
+		dup_iov[TCP_IOV_PAYLOAD].iov_len = l4len;
 	}
 
 	if (CONN_V4(conn)) {
@@ -350,8 +352,10 @@ static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn *conn,
 		}
 
 		tcp4_frame_conns[tcp4_payload_used] = conn;
-
-		iov = tcp4_l2_iov[tcp4_payload_used++];
+		iov = tcp4_l2_iov[tcp4_payload_used];
+		iov[TCP_IOV_IP] =
+			IOV_OF_LVALUE(tcp4_payload_ip[tcp4_payload_used++]);
+		iov[TCP_IOV_ETH].iov_base = &tcp4_eth_src;
 		l4len = tcp_l2_buf_fill_headers(conn, iov, dlen, check, seq,
 						false);
 		iov[TCP_IOV_PAYLOAD].iov_len = l4len;
@@ -359,8 +363,10 @@ static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn *conn,
 			tcp_payload_flush(c);
 	} else if (CONN_V6(conn)) {
 		tcp6_frame_conns[tcp6_payload_used] = conn;
-
-		iov = tcp6_l2_iov[tcp6_payload_used++];
+		iov = tcp6_l2_iov[tcp6_payload_used];
+		iov[TCP_IOV_IP] =
+			IOV_OF_LVALUE(tcp6_payload_ip[tcp6_payload_used++]);
+		iov[TCP_IOV_ETH].iov_base = &tcp6_eth_src;
 		l4len = tcp_l2_buf_fill_headers(conn, iov, dlen, NULL, seq,
 						false);
 		iov[TCP_IOV_PAYLOAD].iov_len = l4len;
-- 
@@ -130,8 +130,7 @@ void tcp_sock4_iov_init(const struct ctx *c)
 		iov = tcp4_l2_iov[i];
 
 		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp4_payload_tap_hdr[i]);
-		iov[TCP_IOV_ETH] = IOV_OF_LVALUE(tcp4_eth_src);
-		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_payload_ip[i]);
+		iov[TCP_IOV_ETH].iov_len = sizeof(struct ethhdr);
 		iov[TCP_IOV_PAYLOAD].iov_base = &tcp4_payload[i];
 	}
 
@@ -173,8 +172,7 @@ void tcp_sock6_iov_init(const struct ctx *c)
 		iov = tcp6_l2_iov[i];
 
 		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp6_payload_tap_hdr[i]);
-		iov[TCP_IOV_ETH] = IOV_OF_LVALUE(tcp6_eth_src);
-		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_payload_ip[i]);
+		iov[TCP_IOV_ETH].iov_len = sizeof(struct ethhdr);
 		iov[TCP_IOV_PAYLOAD].iov_base = &tcp6_payload[i];
 	}
 
@@ -273,11 +271,17 @@ int tcp_buf_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
 	uint32_t seq;
 	int ret;
 
-	if (CONN_V4(conn))
-		iov = tcp4_l2_flags_iov[tcp4_flags_used++];
-	else
-		iov = tcp6_l2_flags_iov[tcp6_flags_used++];
-
+	if (CONN_V4(conn)) {
+		iov = tcp4_l2_flags_iov[tcp4_flags_used];
+		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_flags_ip[tcp4_flags_used]);
+		iov[TCP_IOV_ETH].iov_base = &tcp4_eth_src;
+		tcp4_flags_used++;
+	} else {
+		iov = tcp6_l2_flags_iov[tcp6_flags_used];
+		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_flags_ip[tcp6_flags_used]);
+		iov[TCP_IOV_ETH].iov_base = &tcp6_eth_src;
+		tcp6_flags_used++;
+	}
 	payload = iov[TCP_IOV_PAYLOAD].iov_base;
 
 	seq = conn->seq_to_tap;
@@ -296,21 +300,19 @@ int tcp_buf_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
 
 	if (flags & DUP_ACK) {
 		struct iovec *dup_iov;
-		int i;
 
 		if (CONN_V4(conn))
 			dup_iov = tcp4_l2_flags_iov[tcp4_flags_used++];
 		else
-			dup_iov = tcp6_l2_flags_iov[tcp6_flags_used++];
-
-		for (i = 0; i < TCP_NUM_IOVS; i++) {
-			/* All frames share the same ethernet header buffer */
-			if (i != TCP_IOV_ETH) {
-				memcpy(dup_iov[i].iov_base, iov[i].iov_base,
-				       iov[i].iov_len);
-			}
-		}
-		dup_iov[TCP_IOV_PAYLOAD].iov_len = iov[TCP_IOV_PAYLOAD].iov_len;
+			dup_iov = tcp4_l2_flags_iov[tcp6_flags_used++];
+
+		memcpy(dup_iov[TCP_IOV_TAP].iov_base, iov[TCP_IOV_TAP].iov_base,
+		       iov[TCP_IOV_TAP].iov_len);
+		dup_iov[TCP_IOV_ETH].iov_base = iov[TCP_IOV_ETH].iov_base;
+		dup_iov[TCP_IOV_IP] = IOV_OF_LVALUE(iov[TCP_IOV_IP]);
+		memcpy(dup_iov[TCP_IOV_PAYLOAD].iov_base,
+		       iov[TCP_IOV_PAYLOAD].iov_base, l4len);
+		dup_iov[TCP_IOV_PAYLOAD].iov_len = l4len;
 	}
 
 	if (CONN_V4(conn)) {
@@ -350,8 +352,10 @@ static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn *conn,
 		}
 
 		tcp4_frame_conns[tcp4_payload_used] = conn;
-
-		iov = tcp4_l2_iov[tcp4_payload_used++];
+		iov = tcp4_l2_iov[tcp4_payload_used];
+		iov[TCP_IOV_IP] =
+			IOV_OF_LVALUE(tcp4_payload_ip[tcp4_payload_used++]);
+		iov[TCP_IOV_ETH].iov_base = &tcp4_eth_src;
 		l4len = tcp_l2_buf_fill_headers(conn, iov, dlen, check, seq,
 						false);
 		iov[TCP_IOV_PAYLOAD].iov_len = l4len;
@@ -359,8 +363,10 @@ static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn *conn,
 			tcp_payload_flush(c);
 	} else if (CONN_V6(conn)) {
 		tcp6_frame_conns[tcp6_payload_used] = conn;
-
-		iov = tcp6_l2_iov[tcp6_payload_used++];
+		iov = tcp6_l2_iov[tcp6_payload_used];
+		iov[TCP_IOV_IP] =
+			IOV_OF_LVALUE(tcp6_payload_ip[tcp6_payload_used++]);
+		iov[TCP_IOV_ETH].iov_base = &tcp6_eth_src;
 		l4len = tcp_l2_buf_fill_headers(conn, iov, dlen, NULL, seq,
 						false);
 		iov[TCP_IOV_PAYLOAD].iov_len = l4len;
-- 
2.45.2

Re: [PATCH v4 1/2] tcp: set ip and eth headers in l2 tap queues on the fly

[David Gibson]

[-- Attachment #1: Type: text/plain, Size: 5539 bytes --]

On Fri, Oct 11, 2024 at 02:35:39PM -0400, Jon Maloy wrote:
> l2 tap queue entries are currently initialized at system start, and
> reused with preset headers through its whole life time. The only
> fields we need to update per message are things like payload size
> and checksums.
> 
> If we want to reuse these entries between ipv4 and ipv6 messages we
> will need to set the pointer to the right header on the fly per
> message, since the header type may differ between entries in the same
> queue.
> 
> The same needs to be done for the ethernet header.
> 
> We do these changes here.
> 
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>
> 
> ---
> v2: Setting pointers to pre-initialized IP and MAC headers instead of
>     copying them in on the fly.
> v3: Adapted to D. Gibson's recent commit eliminitaing overlapping memcpy()
> ---
>  tcp_buf.c | 54 ++++++++++++++++++++++++++++++------------------------
>  1 file changed, 30 insertions(+), 24 deletions(-)
> 
> diff --git a/tcp_buf.c b/tcp_buf.c
> index 238827b..e4fa59f 100644
> --- a/tcp_buf.c
> +++ b/tcp_buf.c
> @@ -130,8 +130,7 @@ void tcp_sock4_iov_init(const struct ctx *c)
>  		iov = tcp4_l2_iov[i];
>  
>  		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp4_payload_tap_hdr[i]);
> -		iov[TCP_IOV_ETH] = IOV_OF_LVALUE(tcp4_eth_src);
> -		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_payload_ip[i]);
> +		iov[TCP_IOV_ETH].iov_len = sizeof(struct ethhdr);
>  		iov[TCP_IOV_PAYLOAD].iov_base = &tcp4_payload[i];
>  	}
>  
> @@ -173,8 +172,7 @@ void tcp_sock6_iov_init(const struct ctx *c)
>  		iov = tcp6_l2_iov[i];
>  
>  		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp6_payload_tap_hdr[i]);
> -		iov[TCP_IOV_ETH] = IOV_OF_LVALUE(tcp6_eth_src);
> -		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_payload_ip[i]);
> +		iov[TCP_IOV_ETH].iov_len = sizeof(struct ethhdr);
>  		iov[TCP_IOV_PAYLOAD].iov_base = &tcp6_payload[i];
>  	}
>  
> @@ -273,11 +271,17 @@ int tcp_buf_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
>  	uint32_t seq;
>  	int ret;
>  
> -	if (CONN_V4(conn))
> -		iov = tcp4_l2_flags_iov[tcp4_flags_used++];
> -	else
> -		iov = tcp6_l2_flags_iov[tcp6_flags_used++];
> -
> +	if (CONN_V4(conn)) {
> +		iov = tcp4_l2_flags_iov[tcp4_flags_used];
> +		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_flags_ip[tcp4_flags_used]);
> +		iov[TCP_IOV_ETH].iov_base = &tcp4_eth_src;
> +		tcp4_flags_used++;
> +	} else {
> +		iov = tcp6_l2_flags_iov[tcp6_flags_used];
> +		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_flags_ip[tcp6_flags_used]);
> +		iov[TCP_IOV_ETH].iov_base = &tcp6_eth_src;
> +		tcp6_flags_used++;
> +	}
>  	payload = iov[TCP_IOV_PAYLOAD].iov_base;
>  
>  	seq = conn->seq_to_tap;
> @@ -296,21 +300,19 @@ int tcp_buf_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
>  
>  	if (flags & DUP_ACK) {
>  		struct iovec *dup_iov;
> -		int i;
>  
>  		if (CONN_V4(conn))
>  			dup_iov = tcp4_l2_flags_iov[tcp4_flags_used++];
>  		else
> -			dup_iov = tcp6_l2_flags_iov[tcp6_flags_used++];
> -
> -		for (i = 0; i < TCP_NUM_IOVS; i++) {
> -			/* All frames share the same ethernet header buffer */
> -			if (i != TCP_IOV_ETH) {
> -				memcpy(dup_iov[i].iov_base, iov[i].iov_base,
> -				       iov[i].iov_len);
> -			}
> -		}
> -		dup_iov[TCP_IOV_PAYLOAD].iov_len = iov[TCP_IOV_PAYLOAD].iov_len;
> +			dup_iov = tcp4_l2_flags_iov[tcp6_flags_used++];

This should be tcp6_l2_flags_iov[], no?  I guess it will become when
the arrays are merged in a subsequent patch.

> +
> +		memcpy(dup_iov[TCP_IOV_TAP].iov_base, iov[TCP_IOV_TAP].iov_base,
> +		       iov[TCP_IOV_TAP].iov_len);
> +		dup_iov[TCP_IOV_ETH].iov_base = iov[TCP_IOV_ETH].iov_base;
> +		dup_iov[TCP_IOV_IP] = IOV_OF_LVALUE(iov[TCP_IOV_IP]);

This should be:
		dup_iov[TCP_IOV_IP] = iov[TCP_IOV_IP];

IOV_OF_LVALUE() won't work because you don't have a sized lvalue to
use.  In fact, I think this will make the dup packet's IP header have
the contents of the struct iovec pointing at the original header,
which is clearly nonsense.

> +		memcpy(dup_iov[TCP_IOV_PAYLOAD].iov_base,
> +		       iov[TCP_IOV_PAYLOAD].iov_base, l4len);
> +		dup_iov[TCP_IOV_PAYLOAD].iov_len = l4len;
>  	}
>  
>  	if (CONN_V4(conn)) {
> @@ -350,8 +352,10 @@ static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn *conn,
>  		}
>  
>  		tcp4_frame_conns[tcp4_payload_used] = conn;
> -
> -		iov = tcp4_l2_iov[tcp4_payload_used++];
> +		iov = tcp4_l2_iov[tcp4_payload_used];
> +		iov[TCP_IOV_IP] =
> +			IOV_OF_LVALUE(tcp4_payload_ip[tcp4_payload_used++]);
> +		iov[TCP_IOV_ETH].iov_base = &tcp4_eth_src;
>  		l4len = tcp_l2_buf_fill_headers(conn, iov, dlen, check, seq,
>  						false);
>  		iov[TCP_IOV_PAYLOAD].iov_len = l4len;
> @@ -359,8 +363,10 @@ static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn *conn,
>  			tcp_payload_flush(c);
>  	} else if (CONN_V6(conn)) {
>  		tcp6_frame_conns[tcp6_payload_used] = conn;
> -
> -		iov = tcp6_l2_iov[tcp6_payload_used++];
> +		iov = tcp6_l2_iov[tcp6_payload_used];
> +		iov[TCP_IOV_IP] =
> +			IOV_OF_LVALUE(tcp6_payload_ip[tcp6_payload_used++]);
> +		iov[TCP_IOV_ETH].iov_base = &tcp6_eth_src;
>  		l4len = tcp_l2_buf_fill_headers(conn, iov, dlen, NULL, seq,
>  						false);
>  		iov[TCP_IOV_PAYLOAD].iov_len = l4len;

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

[PATCH v4 2/2] tcp: unify l2 TCPv4 and TCPv6 queues and structures

[Jon Maloy]

Following the preparations in the previous commit, we can now remove
the payload and flag queues dedicated for TCPv6 and TCPv4 and move all
traffic into common queues handling both protocol types.

Apart from reducing code and memory footprint, this change reduces
a potential risk for TCPv4 traffic starving out TCPv6 traffic.
Since we always flush out the TCPv4 frame queue before the TCPv6 queue,
the latter will never be handled if the former fails to send all its
frames.

Tests with iperf3 shows no measurable change in performance after this
change.

Signed-off-by: Jon Maloy <jmaloy@redhat.com>

---
    v2: Merged previous patch #3, where the tcp4_ prefix was changed to
        tcp_ into this patch.
    v3: Fixes based on feedback from D. Gibson
    v4: Rebased to latest version on master branch
---
 tcp.c     |   6 +-
 tcp_buf.c | 246 ++++++++++++++++--------------------------------------
 tcp_buf.h |   3 +-
 3 files changed, 75 insertions(+), 180 deletions(-)

diff --git a/tcp.c b/tcp.c
index 9617b7a..1509130 100644
--- a/tcp.c
+++ b/tcp.c
@@ -2632,11 +2632,7 @@ int tcp_init(struct ctx *c)
 {
 	ASSERT(!c->no_tcp);
 
-	if (c->ifi4)
-		tcp_sock4_iov_init(c);
-
-	if (c->ifi6)
-		tcp_sock6_iov_init(c);
+	tcp_sock_iov_init(c);
 
 	memset(init_sock_pool4,		0xff,	sizeof(init_sock_pool4));
 	memset(init_sock_pool6,		0xff,	sizeof(init_sock_pool6));
diff --git a/tcp_buf.c b/tcp_buf.c
index e4fa59f..487f677 100644
--- a/tcp_buf.c
+++ b/tcp_buf.c
@@ -38,59 +38,44 @@
 	(c->mode == MODE_PASTA ? 1 : TCP_FRAMES_MEM)
 
 /* Static buffers */
-/* Ethernet header for IPv4 frames */
+
+/* Ethernet header for IPv4 and IPv6 frames */
 static struct ethhdr		tcp4_eth_src;
+static struct ethhdr		tcp6_eth_src;
+
+static struct tap_hdr		tcp_payload_tap_hdr[TCP_FRAMES_MEM];
+
+/* IP headers for IPv4 and IPv6 */
+struct iphdr		tcp4_payload_ip[TCP_FRAMES_MEM];
+struct ipv6hdr		tcp6_payload_ip[TCP_FRAMES_MEM];
 
-static struct tap_hdr		tcp4_payload_tap_hdr[TCP_FRAMES_MEM];
-/* IPv4 headers */
-static struct iphdr		tcp4_payload_ip[TCP_FRAMES_MEM];
-/* TCP segments with payload for IPv4 frames */
-static struct tcp_payload_t	tcp4_payload[TCP_FRAMES_MEM];
+/* TCP segments with payload for IPv4 and IPv6 frames */
+static struct tcp_payload_t	tcp_payload[TCP_FRAMES_MEM];
 
-static_assert(MSS4 <= sizeof(tcp4_payload[0].data), "MSS4 is greater than 65516");
+static_assert(MSS4 <= sizeof(tcp_payload[0].data), "MSS4 is greater than 65516");
+static_assert(MSS6 <= sizeof(tcp_payload[0].data), "MSS6 is greater than 65516");
 
 /* References tracking the owner connection of frames in the tap outqueue */
-static struct tcp_tap_conn *tcp4_frame_conns[TCP_FRAMES_MEM];
-static unsigned int tcp4_payload_used;
+static struct tcp_tap_conn *tcp_frame_conns[TCP_FRAMES_MEM];
+static unsigned int tcp_payload_used;
 
-static struct tap_hdr		tcp4_flags_tap_hdr[TCP_FRAMES_MEM];
+static struct tap_hdr		tcp_flags_tap_hdr[TCP_FRAMES_MEM];
 /* IPv4 headers for TCP segment without payload */
 static struct iphdr		tcp4_flags_ip[TCP_FRAMES_MEM];
 /* TCP segments without payload for IPv4 frames */
-static struct tcp_flags_t	tcp4_flags[TCP_FRAMES_MEM];
-
-static unsigned int tcp4_flags_used;
-
-/* Ethernet header for IPv6 frames */
-static struct ethhdr		tcp6_eth_src;
-
-static struct tap_hdr		tcp6_payload_tap_hdr[TCP_FRAMES_MEM];
-/* IPv6 headers */
-static struct ipv6hdr		tcp6_payload_ip[TCP_FRAMES_MEM];
-/* TCP headers and data for IPv6 frames */
-static struct tcp_payload_t	tcp6_payload[TCP_FRAMES_MEM];
+static struct tcp_flags_t	tcp_flags[TCP_FRAMES_MEM];
 
-static_assert(MSS6 <= sizeof(tcp6_payload[0].data), "MSS6 is greater than 65516");
+static unsigned int tcp_flags_used;
 
-/* References tracking the owner connection of frames in the tap outqueue */
-static struct tcp_tap_conn *tcp6_frame_conns[TCP_FRAMES_MEM];
-static unsigned int tcp6_payload_used;
-
-static struct tap_hdr		tcp6_flags_tap_hdr[TCP_FRAMES_MEM];
 /* IPv6 headers for TCP segment without payload */
 static struct ipv6hdr		tcp6_flags_ip[TCP_FRAMES_MEM];
-/* TCP segment without payload for IPv6 frames */
-static struct tcp_flags_t	tcp6_flags[TCP_FRAMES_MEM];
-
-static unsigned int tcp6_flags_used;
 
 /* recvmsg()/sendmsg() data for tap */
 static struct iovec	iov_sock		[TCP_FRAMES_MEM + 1];
 
-static struct iovec	tcp4_l2_iov		[TCP_FRAMES_MEM][TCP_NUM_IOVS];
-static struct iovec	tcp6_l2_iov		[TCP_FRAMES_MEM][TCP_NUM_IOVS];
-static struct iovec	tcp4_l2_flags_iov	[TCP_FRAMES_MEM][TCP_NUM_IOVS];
-static struct iovec	tcp6_l2_flags_iov	[TCP_FRAMES_MEM][TCP_NUM_IOVS];
+static struct iovec	tcp_l2_iov[TCP_FRAMES_MEM][TCP_NUM_IOVS];
+static struct iovec	tcp_l2_flags_iov[TCP_FRAMES_MEM][TCP_NUM_IOVS];
+
 /**
  * tcp_update_l2_buf() - Update Ethernet header buffers with addresses
  * @eth_d:	Ethernet destination address, NULL if unchanged
@@ -103,86 +88,46 @@ void tcp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s)
 }
 
 /**
- * tcp_sock4_iov_init() - Initialise scatter-gather L2 buffers for IPv4 sockets
+ * tcp_sock_iov_init() - Initialise scatter-gather L2 buffers for IPv4 sockets
  * @c:		Execution context
  */
-void tcp_sock4_iov_init(const struct ctx *c)
+void tcp_sock_iov_init(const struct ctx *c)
 {
+	struct ipv6hdr ip6 = L2_BUF_IP6_INIT(IPPROTO_TCP);
 	struct iphdr iph = L2_BUF_IP4_INIT(IPPROTO_TCP);
-	struct iovec *iov;
 	int i;
 
+	tcp6_eth_src.h_proto = htons_constant(ETH_P_IPV6);
 	tcp4_eth_src.h_proto = htons_constant(ETH_P_IP);
 
-	for (i = 0; i < ARRAY_SIZE(tcp4_payload); i++) {
+	for (i = 0; i < ARRAY_SIZE(tcp_payload); i++) {
+		tcp6_payload_ip[i] = ip6;
 		tcp4_payload_ip[i] = iph;
-		tcp4_payload[i].th.doff = sizeof(struct tcphdr) / 4;
-		tcp4_payload[i].th.ack = 1;
+		tcp_payload[i].th.doff = sizeof(struct tcphdr) / 4;
+		tcp_payload[i].th.ack = 1;
 	}
 
-	for (i = 0; i < ARRAY_SIZE(tcp4_flags); i++) {
+	for (i = 0; i < ARRAY_SIZE(tcp_flags); i++) {
+		tcp6_flags_ip[i] = ip6;
 		tcp4_flags_ip[i] = iph;
-		tcp4_flags[i].th.doff = sizeof(struct tcphdr) / 4;
-		tcp4_flags[i].th.ack = 1;
+		tcp_flags[i].th.doff = sizeof(struct tcphdr) / 4;
+		tcp_flags[i].th.ack = 1;
 	}
 
 	for (i = 0; i < TCP_FRAMES_MEM; i++) {
-		iov = tcp4_l2_iov[i];
+		struct iovec *iov = tcp_l2_iov[i];
 
-		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp4_payload_tap_hdr[i]);
+		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp_payload_tap_hdr[i]);
 		iov[TCP_IOV_ETH].iov_len = sizeof(struct ethhdr);
-		iov[TCP_IOV_PAYLOAD].iov_base = &tcp4_payload[i];
-	}
-
-	for (i = 0; i < TCP_FRAMES_MEM; i++) {
-		iov = tcp4_l2_flags_iov[i];
-
-		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp4_flags_tap_hdr[i]);
-		iov[TCP_IOV_ETH] = IOV_OF_LVALUE(tcp4_eth_src);
-		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_flags_ip[i]);
-		iov[TCP_IOV_PAYLOAD].iov_base = &tcp4_flags[i];
-	}
-}
-
-/**
- * tcp_sock6_iov_init() - Initialise scatter-gather L2 buffers for IPv6 sockets
- * @c:		Execution context
- */
-void tcp_sock6_iov_init(const struct ctx *c)
-{
-	struct ipv6hdr ip6 = L2_BUF_IP6_INIT(IPPROTO_TCP);
-	struct iovec *iov;
-	int i;
-
-	tcp6_eth_src.h_proto = htons_constant(ETH_P_IPV6);
-
-	for (i = 0; i < ARRAY_SIZE(tcp6_payload); i++) {
-		tcp6_payload_ip[i] = ip6;
-		tcp6_payload[i].th.doff = sizeof(struct tcphdr) / 4;
-		tcp6_payload[i].th.ack = 1;
-	}
-
-	for (i = 0; i < ARRAY_SIZE(tcp6_flags); i++) {
-		tcp6_flags_ip[i] = ip6;
-		tcp6_flags[i].th.doff = sizeof(struct tcphdr) / 4;
-		tcp6_flags[i].th .ack = 1;
+		iov[TCP_IOV_PAYLOAD].iov_base = &tcp_payload[i];
 	}
 
 	for (i = 0; i < TCP_FRAMES_MEM; i++) {
-		iov = tcp6_l2_iov[i];
+		struct iovec *iov = tcp_l2_flags_iov[i];
 
-		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp6_payload_tap_hdr[i]);
+		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp_flags_tap_hdr[i]);
 		iov[TCP_IOV_ETH].iov_len = sizeof(struct ethhdr);
-		iov[TCP_IOV_PAYLOAD].iov_base = &tcp6_payload[i];
-	}
-
-	for (i = 0; i < TCP_FRAMES_MEM; i++) {
-		iov = tcp6_l2_flags_iov[i];
-
-		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp6_flags_tap_hdr[i]);
-		iov[TCP_IOV_ETH] = IOV_OF_LVALUE(tcp6_eth_src);
-		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_flags_ip[i]);
-		iov[TCP_IOV_PAYLOAD].iov_base = &tcp6_flags[i];
+		iov[TCP_IOV_PAYLOAD].iov_base = &tcp_flags[i];
 	}
 }
 
@@ -192,13 +137,9 @@ void tcp_sock6_iov_init(const struct ctx *c)
  */
 void tcp_flags_flush(const struct ctx *c)
 {
-	tap_send_frames(c, &tcp6_l2_flags_iov[0][0], TCP_NUM_IOVS,
-			tcp6_flags_used);
-	tcp6_flags_used = 0;
-
-	tap_send_frames(c, &tcp4_l2_flags_iov[0][0], TCP_NUM_IOVS,
-			tcp4_flags_used);
-	tcp4_flags_used = 0;
+	tap_send_frames(c, &tcp_l2_flags_iov[0][0], TCP_NUM_IOVS,
+			tcp_flags_used);
+	tcp_flags_used = 0;
 }
 
 /**
@@ -237,21 +178,13 @@ void tcp_payload_flush(const struct ctx *c)
 {
 	size_t m;
 
-	m = tap_send_frames(c, &tcp6_l2_iov[0][0], TCP_NUM_IOVS,
-			    tcp6_payload_used);
-	if (m != tcp6_payload_used) {
-		tcp_revert_seq(c, &tcp6_frame_conns[m], &tcp6_l2_iov[m],
-			       tcp6_payload_used - m);
+	m = tap_send_frames(c, &tcp_l2_iov[0][0], TCP_NUM_IOVS,
+			    tcp_payload_used);
+	if (m != tcp_payload_used) {
+		tcp_revert_seq(c, &tcp_frame_conns[m], &tcp_l2_iov[m],
+			       tcp_payload_used - m);
 	}
-	tcp6_payload_used = 0;
-
-	m = tap_send_frames(c, &tcp4_l2_iov[0][0], TCP_NUM_IOVS,
-			    tcp4_payload_used);
-	if (m != tcp4_payload_used) {
-		tcp_revert_seq(c, &tcp4_frame_conns[m], &tcp4_l2_iov[m],
-			       tcp4_payload_used - m);
-	}
-	tcp4_payload_used = 0;
+	tcp_payload_used = 0;
 }
 
 /**
@@ -271,41 +204,30 @@ int tcp_buf_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
 	uint32_t seq;
 	int ret;
 
+	iov = tcp_l2_flags_iov[tcp_flags_used];
 	if (CONN_V4(conn)) {
-		iov = tcp4_l2_flags_iov[tcp4_flags_used];
-		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_flags_ip[tcp4_flags_used]);
+		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_flags_ip[tcp_flags_used]);
 		iov[TCP_IOV_ETH].iov_base = &tcp4_eth_src;
-		tcp4_flags_used++;
 	} else {
-		iov = tcp6_l2_flags_iov[tcp6_flags_used];
-		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_flags_ip[tcp6_flags_used]);
+		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_flags_ip[tcp_flags_used]);
 		iov[TCP_IOV_ETH].iov_base = &tcp6_eth_src;
-		tcp6_flags_used++;
 	}
-	payload = iov[TCP_IOV_PAYLOAD].iov_base;
 
+	payload = iov[TCP_IOV_PAYLOAD].iov_base;
 	seq = conn->seq_to_tap;
 	ret = tcp_prepare_flags(c, conn, flags, &payload->th,
 				payload->opts, &optlen);
-	if (ret <= 0) {
-		if (CONN_V4(conn))
-			tcp4_flags_used--;
-		else
-			tcp6_flags_used--;
+	if (ret <= 0)
 		return ret;
-	}
 
+	tcp_flags_used++;
 	l4len = tcp_l2_buf_fill_headers(conn, iov, optlen, NULL, seq, false);
 	iov[TCP_IOV_PAYLOAD].iov_len = l4len;
 
 	if (flags & DUP_ACK) {
 		struct iovec *dup_iov;
 
-		if (CONN_V4(conn))
-			dup_iov = tcp4_l2_flags_iov[tcp4_flags_used++];
-		else
-			dup_iov = tcp4_l2_flags_iov[tcp6_flags_used++];
-
+		dup_iov = tcp_l2_flags_iov[tcp_flags_used++];
 		memcpy(dup_iov[TCP_IOV_TAP].iov_base, iov[TCP_IOV_TAP].iov_base,
 		       iov[TCP_IOV_TAP].iov_len);
 		dup_iov[TCP_IOV_ETH].iov_base = iov[TCP_IOV_ETH].iov_base;
@@ -315,13 +237,8 @@ int tcp_buf_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
 		dup_iov[TCP_IOV_PAYLOAD].iov_len = l4len;
 	}
 
-	if (CONN_V4(conn)) {
-		if (tcp4_flags_used > TCP_FRAMES_MEM - 2)
-			tcp_flags_flush(c);
-	} else {
-		if (tcp6_flags_used > TCP_FRAMES_MEM - 2)
-			tcp_flags_flush(c);
-	}
+	if (tcp_flags_used > TCP_FRAMES_MEM - 2)
+		tcp_flags_flush(c);
 
 	return 0;
 }
@@ -337,42 +254,30 @@ int tcp_buf_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
 static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn *conn,
 			    ssize_t dlen, int no_csum, uint32_t seq)
 {
+	const uint16_t *check = NULL;
 	struct iovec *iov;
 	size_t l4len;
 
 	conn->seq_to_tap = seq + dlen;
-
+	tcp_frame_conns[tcp_payload_used] = conn;
+	iov = tcp_l2_iov[tcp_payload_used];
 	if (CONN_V4(conn)) {
-		struct iovec *iov_prev = tcp4_l2_iov[tcp4_payload_used - 1];
-		const uint16_t *check = NULL;
-
 		if (no_csum) {
+			struct iovec *iov_prev = tcp_l2_iov[tcp_payload_used - 1];
 			struct iphdr *iph = iov_prev[TCP_IOV_IP].iov_base;
+
 			check = &iph->check;
 		}
-
-		tcp4_frame_conns[tcp4_payload_used] = conn;
-		iov = tcp4_l2_iov[tcp4_payload_used];
-		iov[TCP_IOV_IP] =
-			IOV_OF_LVALUE(tcp4_payload_ip[tcp4_payload_used++]);
+		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_payload_ip[tcp_payload_used]);
 		iov[TCP_IOV_ETH].iov_base = &tcp4_eth_src;
-		l4len = tcp_l2_buf_fill_headers(conn, iov, dlen, check, seq,
-						false);
-		iov[TCP_IOV_PAYLOAD].iov_len = l4len;
-		if (tcp4_payload_used > TCP_FRAMES_MEM - 1)
-			tcp_payload_flush(c);
 	} else if (CONN_V6(conn)) {
-		tcp6_frame_conns[tcp6_payload_used] = conn;
-		iov = tcp6_l2_iov[tcp6_payload_used];
-		iov[TCP_IOV_IP] =
-			IOV_OF_LVALUE(tcp6_payload_ip[tcp6_payload_used++]);
+		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_payload_ip[tcp_payload_used]);
 		iov[TCP_IOV_ETH].iov_base = &tcp6_eth_src;
-		l4len = tcp_l2_buf_fill_headers(conn, iov, dlen, NULL, seq,
-						false);
-		iov[TCP_IOV_PAYLOAD].iov_len = l4len;
-		if (tcp6_payload_used > TCP_FRAMES_MEM - 1)
-			tcp_payload_flush(c);
 	}
+	l4len = tcp_l2_buf_fill_headers(conn, iov, dlen, check, seq, false);
+	iov[TCP_IOV_PAYLOAD].iov_len = l4len;
+	if (++tcp_payload_used > TCP_FRAMES_MEM - 1)
+		tcp_payload_flush(c);
 }
 
 /**
@@ -388,8 +293,7 @@ int tcp_buf_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn)
 {
 	uint32_t wnd_scaled = conn->wnd_from_tap << conn->ws_from_tap;
 	int fill_bufs, send_bufs = 0, last_len, iov_rem = 0;
-	int sendlen, len, dlen, v4 = CONN_V4(conn);
-	int s = conn->sock, i, ret = 0;
+	int sendlen, len, dlen, i, s = conn->sock, ret = 0;
 	struct msghdr mh_sock = { 0 };
 	uint16_t mss = MSS_GET(conn);
 	uint32_t already_sent, seq;
@@ -436,19 +340,15 @@ int tcp_buf_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn)
 		mh_sock.msg_iovlen = fill_bufs;
 	}
 
-	if (( v4 && tcp4_payload_used + fill_bufs > TCP_FRAMES_MEM) ||
-	    (!v4 && tcp6_payload_used + fill_bufs > TCP_FRAMES_MEM)) {
+	if (tcp_payload_used + fill_bufs > TCP_FRAMES_MEM) {
 		tcp_payload_flush(c);
 
 		/* Silence Coverity CWE-125 false positive */
-		tcp4_payload_used = tcp6_payload_used = 0;
+		tcp_payload_used = 0;
 	}
 
 	for (i = 0, iov = iov_sock + 1; i < fill_bufs; i++, iov++) {
-		if (v4)
-			iov->iov_base = &tcp4_payload[tcp4_payload_used + i].data;
-		else
-			iov->iov_base = &tcp6_payload[tcp6_payload_used + i].data;
+		iov->iov_base = &tcp_payload[tcp_payload_used + i].data;
 		iov->iov_len = mss;
 	}
 	if (iov_rem)
@@ -496,7 +396,7 @@ int tcp_buf_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn)
 	dlen = mss;
 	seq = conn->seq_to_tap;
 	for (i = 0; i < send_bufs; i++) {
-		int no_csum = i && i != send_bufs - 1 && tcp4_payload_used;
+		int no_csum = i && i != send_bufs - 1 && tcp_payload_used;
 
 		if (i == send_bufs - 1)
 			dlen = last_len;
diff --git a/tcp_buf.h b/tcp_buf.h
index 8d4b615..49c04d4 100644
--- a/tcp_buf.h
+++ b/tcp_buf.h
@@ -6,8 +6,7 @@
 #ifndef TCP_BUF_H
 #define TCP_BUF_H
 
-void tcp_sock4_iov_init(const struct ctx *c);
-void tcp_sock6_iov_init(const struct ctx *c);
+void tcp_sock_iov_init(const struct ctx *c);
 void tcp_flags_flush(const struct ctx *c);
 void tcp_payload_flush(const struct ctx *c);
 int tcp_buf_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn);
-- 
@@ -6,8 +6,7 @@
 #ifndef TCP_BUF_H
 #define TCP_BUF_H
 
-void tcp_sock4_iov_init(const struct ctx *c);
-void tcp_sock6_iov_init(const struct ctx *c);
+void tcp_sock_iov_init(const struct ctx *c);
 void tcp_flags_flush(const struct ctx *c);
 void tcp_payload_flush(const struct ctx *c);
 int tcp_buf_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn);
-- 
2.45.2

Re: [PATCH v4 2/2] tcp: unify l2 TCPv4 and TCPv6 queues and structures

[David Gibson]

[-- Attachment #1: Type: text/plain, Size: 17145 bytes --]

On Fri, Oct 11, 2024 at 02:35:40PM -0400, Jon Maloy wrote:
> Following the preparations in the previous commit, we can now remove
> the payload and flag queues dedicated for TCPv6 and TCPv4 and move all
> traffic into common queues handling both protocol types.
> 
> Apart from reducing code and memory footprint, this change reduces
> a potential risk for TCPv4 traffic starving out TCPv6 traffic.
> Since we always flush out the TCPv4 frame queue before the TCPv6 queue,
> the latter will never be handled if the former fails to send all its
> frames.
> 
> Tests with iperf3 shows no measurable change in performance after this
> change.
> 
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

With the caveat that of course it will need to be rebased on a new
version of 1/2 with the small but serious bug fixed.

> 
> ---
>     v2: Merged previous patch #3, where the tcp4_ prefix was changed to
>         tcp_ into this patch.
>     v3: Fixes based on feedback from D. Gibson
>     v4: Rebased to latest version on master branch
> ---
>  tcp.c     |   6 +-
>  tcp_buf.c | 246 ++++++++++++++++--------------------------------------
>  tcp_buf.h |   3 +-
>  3 files changed, 75 insertions(+), 180 deletions(-)
> 
> diff --git a/tcp.c b/tcp.c
> index 9617b7a..1509130 100644
> --- a/tcp.c
> +++ b/tcp.c
> @@ -2632,11 +2632,7 @@ int tcp_init(struct ctx *c)
>  {
>  	ASSERT(!c->no_tcp);
>  
> -	if (c->ifi4)
> -		tcp_sock4_iov_init(c);
> -
> -	if (c->ifi6)
> -		tcp_sock6_iov_init(c);
> +	tcp_sock_iov_init(c);
>  
>  	memset(init_sock_pool4,		0xff,	sizeof(init_sock_pool4));
>  	memset(init_sock_pool6,		0xff,	sizeof(init_sock_pool6));
> diff --git a/tcp_buf.c b/tcp_buf.c
> index e4fa59f..487f677 100644
> --- a/tcp_buf.c
> +++ b/tcp_buf.c
> @@ -38,59 +38,44 @@
>  	(c->mode == MODE_PASTA ? 1 : TCP_FRAMES_MEM)
>  
>  /* Static buffers */
> -/* Ethernet header for IPv4 frames */
> +
> +/* Ethernet header for IPv4 and IPv6 frames */
>  static struct ethhdr		tcp4_eth_src;
> +static struct ethhdr		tcp6_eth_src;
> +
> +static struct tap_hdr		tcp_payload_tap_hdr[TCP_FRAMES_MEM];
> +
> +/* IP headers for IPv4 and IPv6 */
> +struct iphdr		tcp4_payload_ip[TCP_FRAMES_MEM];
> +struct ipv6hdr		tcp6_payload_ip[TCP_FRAMES_MEM];
>  
> -static struct tap_hdr		tcp4_payload_tap_hdr[TCP_FRAMES_MEM];
> -/* IPv4 headers */
> -static struct iphdr		tcp4_payload_ip[TCP_FRAMES_MEM];
> -/* TCP segments with payload for IPv4 frames */
> -static struct tcp_payload_t	tcp4_payload[TCP_FRAMES_MEM];
> +/* TCP segments with payload for IPv4 and IPv6 frames */
> +static struct tcp_payload_t	tcp_payload[TCP_FRAMES_MEM];
>  
> -static_assert(MSS4 <= sizeof(tcp4_payload[0].data), "MSS4 is greater than 65516");
> +static_assert(MSS4 <= sizeof(tcp_payload[0].data), "MSS4 is greater than 65516");
> +static_assert(MSS6 <= sizeof(tcp_payload[0].data), "MSS6 is greater than 65516");
>  
>  /* References tracking the owner connection of frames in the tap outqueue */
> -static struct tcp_tap_conn *tcp4_frame_conns[TCP_FRAMES_MEM];
> -static unsigned int tcp4_payload_used;
> +static struct tcp_tap_conn *tcp_frame_conns[TCP_FRAMES_MEM];
> +static unsigned int tcp_payload_used;
>  
> -static struct tap_hdr		tcp4_flags_tap_hdr[TCP_FRAMES_MEM];
> +static struct tap_hdr		tcp_flags_tap_hdr[TCP_FRAMES_MEM];
>  /* IPv4 headers for TCP segment without payload */
>  static struct iphdr		tcp4_flags_ip[TCP_FRAMES_MEM];
>  /* TCP segments without payload for IPv4 frames */
> -static struct tcp_flags_t	tcp4_flags[TCP_FRAMES_MEM];
> -
> -static unsigned int tcp4_flags_used;
> -
> -/* Ethernet header for IPv6 frames */
> -static struct ethhdr		tcp6_eth_src;
> -
> -static struct tap_hdr		tcp6_payload_tap_hdr[TCP_FRAMES_MEM];
> -/* IPv6 headers */
> -static struct ipv6hdr		tcp6_payload_ip[TCP_FRAMES_MEM];
> -/* TCP headers and data for IPv6 frames */
> -static struct tcp_payload_t	tcp6_payload[TCP_FRAMES_MEM];
> +static struct tcp_flags_t	tcp_flags[TCP_FRAMES_MEM];
>  
> -static_assert(MSS6 <= sizeof(tcp6_payload[0].data), "MSS6 is greater than 65516");
> +static unsigned int tcp_flags_used;
>  
> -/* References tracking the owner connection of frames in the tap outqueue */
> -static struct tcp_tap_conn *tcp6_frame_conns[TCP_FRAMES_MEM];
> -static unsigned int tcp6_payload_used;
> -
> -static struct tap_hdr		tcp6_flags_tap_hdr[TCP_FRAMES_MEM];
>  /* IPv6 headers for TCP segment without payload */
>  static struct ipv6hdr		tcp6_flags_ip[TCP_FRAMES_MEM];
> -/* TCP segment without payload for IPv6 frames */
> -static struct tcp_flags_t	tcp6_flags[TCP_FRAMES_MEM];
> -
> -static unsigned int tcp6_flags_used;
>  
>  /* recvmsg()/sendmsg() data for tap */
>  static struct iovec	iov_sock		[TCP_FRAMES_MEM + 1];
>  
> -static struct iovec	tcp4_l2_iov		[TCP_FRAMES_MEM][TCP_NUM_IOVS];
> -static struct iovec	tcp6_l2_iov		[TCP_FRAMES_MEM][TCP_NUM_IOVS];
> -static struct iovec	tcp4_l2_flags_iov	[TCP_FRAMES_MEM][TCP_NUM_IOVS];
> -static struct iovec	tcp6_l2_flags_iov	[TCP_FRAMES_MEM][TCP_NUM_IOVS];
> +static struct iovec	tcp_l2_iov[TCP_FRAMES_MEM][TCP_NUM_IOVS];
> +static struct iovec	tcp_l2_flags_iov[TCP_FRAMES_MEM][TCP_NUM_IOVS];
> +
>  /**
>   * tcp_update_l2_buf() - Update Ethernet header buffers with addresses
>   * @eth_d:	Ethernet destination address, NULL if unchanged
> @@ -103,86 +88,46 @@ void tcp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s)
>  }
>  
>  /**
> - * tcp_sock4_iov_init() - Initialise scatter-gather L2 buffers for IPv4 sockets
> + * tcp_sock_iov_init() - Initialise scatter-gather L2 buffers for IPv4 sockets
>   * @c:		Execution context
>   */
> -void tcp_sock4_iov_init(const struct ctx *c)
> +void tcp_sock_iov_init(const struct ctx *c)
>  {
> +	struct ipv6hdr ip6 = L2_BUF_IP6_INIT(IPPROTO_TCP);
>  	struct iphdr iph = L2_BUF_IP4_INIT(IPPROTO_TCP);
> -	struct iovec *iov;
>  	int i;
>  
> +	tcp6_eth_src.h_proto = htons_constant(ETH_P_IPV6);
>  	tcp4_eth_src.h_proto = htons_constant(ETH_P_IP);
>  
> -	for (i = 0; i < ARRAY_SIZE(tcp4_payload); i++) {
> +	for (i = 0; i < ARRAY_SIZE(tcp_payload); i++) {
> +		tcp6_payload_ip[i] = ip6;
>  		tcp4_payload_ip[i] = iph;
> -		tcp4_payload[i].th.doff = sizeof(struct tcphdr) / 4;
> -		tcp4_payload[i].th.ack = 1;
> +		tcp_payload[i].th.doff = sizeof(struct tcphdr) / 4;
> +		tcp_payload[i].th.ack = 1;
>  	}
>  
> -	for (i = 0; i < ARRAY_SIZE(tcp4_flags); i++) {
> +	for (i = 0; i < ARRAY_SIZE(tcp_flags); i++) {
> +		tcp6_flags_ip[i] = ip6;
>  		tcp4_flags_ip[i] = iph;
> -		tcp4_flags[i].th.doff = sizeof(struct tcphdr) / 4;
> -		tcp4_flags[i].th.ack = 1;
> +		tcp_flags[i].th.doff = sizeof(struct tcphdr) / 4;
> +		tcp_flags[i].th.ack = 1;
>  	}
>  
>  	for (i = 0; i < TCP_FRAMES_MEM; i++) {
> -		iov = tcp4_l2_iov[i];
> +		struct iovec *iov = tcp_l2_iov[i];
>  
> -		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp4_payload_tap_hdr[i]);
> +		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp_payload_tap_hdr[i]);
>  		iov[TCP_IOV_ETH].iov_len = sizeof(struct ethhdr);
> -		iov[TCP_IOV_PAYLOAD].iov_base = &tcp4_payload[i];
> -	}
> -
> -	for (i = 0; i < TCP_FRAMES_MEM; i++) {
> -		iov = tcp4_l2_flags_iov[i];
> -
> -		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp4_flags_tap_hdr[i]);
> -		iov[TCP_IOV_ETH] = IOV_OF_LVALUE(tcp4_eth_src);
> -		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_flags_ip[i]);
> -		iov[TCP_IOV_PAYLOAD].iov_base = &tcp4_flags[i];
> -	}
> -}
> -
> -/**
> - * tcp_sock6_iov_init() - Initialise scatter-gather L2 buffers for IPv6 sockets
> - * @c:		Execution context
> - */
> -void tcp_sock6_iov_init(const struct ctx *c)
> -{
> -	struct ipv6hdr ip6 = L2_BUF_IP6_INIT(IPPROTO_TCP);
> -	struct iovec *iov;
> -	int i;
> -
> -	tcp6_eth_src.h_proto = htons_constant(ETH_P_IPV6);
> -
> -	for (i = 0; i < ARRAY_SIZE(tcp6_payload); i++) {
> -		tcp6_payload_ip[i] = ip6;
> -		tcp6_payload[i].th.doff = sizeof(struct tcphdr) / 4;
> -		tcp6_payload[i].th.ack = 1;
> -	}
> -
> -	for (i = 0; i < ARRAY_SIZE(tcp6_flags); i++) {
> -		tcp6_flags_ip[i] = ip6;
> -		tcp6_flags[i].th.doff = sizeof(struct tcphdr) / 4;
> -		tcp6_flags[i].th .ack = 1;
> +		iov[TCP_IOV_PAYLOAD].iov_base = &tcp_payload[i];
>  	}
>  
>  	for (i = 0; i < TCP_FRAMES_MEM; i++) {
> -		iov = tcp6_l2_iov[i];
> +		struct iovec *iov = tcp_l2_flags_iov[i];
>  
> -		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp6_payload_tap_hdr[i]);
> +		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp_flags_tap_hdr[i]);
>  		iov[TCP_IOV_ETH].iov_len = sizeof(struct ethhdr);
> -		iov[TCP_IOV_PAYLOAD].iov_base = &tcp6_payload[i];
> -	}
> -
> -	for (i = 0; i < TCP_FRAMES_MEM; i++) {
> -		iov = tcp6_l2_flags_iov[i];
> -
> -		iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp6_flags_tap_hdr[i]);
> -		iov[TCP_IOV_ETH] = IOV_OF_LVALUE(tcp6_eth_src);
> -		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_flags_ip[i]);
> -		iov[TCP_IOV_PAYLOAD].iov_base = &tcp6_flags[i];
> +		iov[TCP_IOV_PAYLOAD].iov_base = &tcp_flags[i];
>  	}
>  }
>  
> @@ -192,13 +137,9 @@ void tcp_sock6_iov_init(const struct ctx *c)
>   */
>  void tcp_flags_flush(const struct ctx *c)
>  {
> -	tap_send_frames(c, &tcp6_l2_flags_iov[0][0], TCP_NUM_IOVS,
> -			tcp6_flags_used);
> -	tcp6_flags_used = 0;
> -
> -	tap_send_frames(c, &tcp4_l2_flags_iov[0][0], TCP_NUM_IOVS,
> -			tcp4_flags_used);
> -	tcp4_flags_used = 0;
> +	tap_send_frames(c, &tcp_l2_flags_iov[0][0], TCP_NUM_IOVS,
> +			tcp_flags_used);
> +	tcp_flags_used = 0;
>  }
>  
>  /**
> @@ -237,21 +178,13 @@ void tcp_payload_flush(const struct ctx *c)
>  {
>  	size_t m;
>  
> -	m = tap_send_frames(c, &tcp6_l2_iov[0][0], TCP_NUM_IOVS,
> -			    tcp6_payload_used);
> -	if (m != tcp6_payload_used) {
> -		tcp_revert_seq(c, &tcp6_frame_conns[m], &tcp6_l2_iov[m],
> -			       tcp6_payload_used - m);
> +	m = tap_send_frames(c, &tcp_l2_iov[0][0], TCP_NUM_IOVS,
> +			    tcp_payload_used);
> +	if (m != tcp_payload_used) {
> +		tcp_revert_seq(c, &tcp_frame_conns[m], &tcp_l2_iov[m],
> +			       tcp_payload_used - m);
>  	}
> -	tcp6_payload_used = 0;
> -
> -	m = tap_send_frames(c, &tcp4_l2_iov[0][0], TCP_NUM_IOVS,
> -			    tcp4_payload_used);
> -	if (m != tcp4_payload_used) {
> -		tcp_revert_seq(c, &tcp4_frame_conns[m], &tcp4_l2_iov[m],
> -			       tcp4_payload_used - m);
> -	}
> -	tcp4_payload_used = 0;
> +	tcp_payload_used = 0;
>  }
>  
>  /**
> @@ -271,41 +204,30 @@ int tcp_buf_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
>  	uint32_t seq;
>  	int ret;
>  
> +	iov = tcp_l2_flags_iov[tcp_flags_used];
>  	if (CONN_V4(conn)) {
> -		iov = tcp4_l2_flags_iov[tcp4_flags_used];
> -		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_flags_ip[tcp4_flags_used]);
> +		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_flags_ip[tcp_flags_used]);
>  		iov[TCP_IOV_ETH].iov_base = &tcp4_eth_src;
> -		tcp4_flags_used++;
>  	} else {
> -		iov = tcp6_l2_flags_iov[tcp6_flags_used];
> -		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_flags_ip[tcp6_flags_used]);
> +		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_flags_ip[tcp_flags_used]);
>  		iov[TCP_IOV_ETH].iov_base = &tcp6_eth_src;
> -		tcp6_flags_used++;
>  	}
> -	payload = iov[TCP_IOV_PAYLOAD].iov_base;
>  
> +	payload = iov[TCP_IOV_PAYLOAD].iov_base;
>  	seq = conn->seq_to_tap;
>  	ret = tcp_prepare_flags(c, conn, flags, &payload->th,
>  				payload->opts, &optlen);
> -	if (ret <= 0) {
> -		if (CONN_V4(conn))
> -			tcp4_flags_used--;
> -		else
> -			tcp6_flags_used--;
> +	if (ret <= 0)
>  		return ret;
> -	}
>  
> +	tcp_flags_used++;
>  	l4len = tcp_l2_buf_fill_headers(conn, iov, optlen, NULL, seq, false);
>  	iov[TCP_IOV_PAYLOAD].iov_len = l4len;
>  
>  	if (flags & DUP_ACK) {
>  		struct iovec *dup_iov;
>  
> -		if (CONN_V4(conn))
> -			dup_iov = tcp4_l2_flags_iov[tcp4_flags_used++];
> -		else
> -			dup_iov = tcp4_l2_flags_iov[tcp6_flags_used++];
> -
> +		dup_iov = tcp_l2_flags_iov[tcp_flags_used++];
>  		memcpy(dup_iov[TCP_IOV_TAP].iov_base, iov[TCP_IOV_TAP].iov_base,
>  		       iov[TCP_IOV_TAP].iov_len);
>  		dup_iov[TCP_IOV_ETH].iov_base = iov[TCP_IOV_ETH].iov_base;
> @@ -315,13 +237,8 @@ int tcp_buf_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
>  		dup_iov[TCP_IOV_PAYLOAD].iov_len = l4len;
>  	}
>  
> -	if (CONN_V4(conn)) {
> -		if (tcp4_flags_used > TCP_FRAMES_MEM - 2)
> -			tcp_flags_flush(c);
> -	} else {
> -		if (tcp6_flags_used > TCP_FRAMES_MEM - 2)
> -			tcp_flags_flush(c);
> -	}
> +	if (tcp_flags_used > TCP_FRAMES_MEM - 2)
> +		tcp_flags_flush(c);
>  
>  	return 0;
>  }
> @@ -337,42 +254,30 @@ int tcp_buf_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
>  static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn *conn,
>  			    ssize_t dlen, int no_csum, uint32_t seq)
>  {
> +	const uint16_t *check = NULL;
>  	struct iovec *iov;
>  	size_t l4len;
>  
>  	conn->seq_to_tap = seq + dlen;
> -
> +	tcp_frame_conns[tcp_payload_used] = conn;
> +	iov = tcp_l2_iov[tcp_payload_used];
>  	if (CONN_V4(conn)) {
> -		struct iovec *iov_prev = tcp4_l2_iov[tcp4_payload_used - 1];
> -		const uint16_t *check = NULL;
> -
>  		if (no_csum) {
> +			struct iovec *iov_prev = tcp_l2_iov[tcp_payload_used - 1];
>  			struct iphdr *iph = iov_prev[TCP_IOV_IP].iov_base;
> +
>  			check = &iph->check;
>  		}
> -
> -		tcp4_frame_conns[tcp4_payload_used] = conn;
> -		iov = tcp4_l2_iov[tcp4_payload_used];
> -		iov[TCP_IOV_IP] =
> -			IOV_OF_LVALUE(tcp4_payload_ip[tcp4_payload_used++]);
> +		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_payload_ip[tcp_payload_used]);
>  		iov[TCP_IOV_ETH].iov_base = &tcp4_eth_src;
> -		l4len = tcp_l2_buf_fill_headers(conn, iov, dlen, check, seq,
> -						false);
> -		iov[TCP_IOV_PAYLOAD].iov_len = l4len;
> -		if (tcp4_payload_used > TCP_FRAMES_MEM - 1)
> -			tcp_payload_flush(c);
>  	} else if (CONN_V6(conn)) {
> -		tcp6_frame_conns[tcp6_payload_used] = conn;
> -		iov = tcp6_l2_iov[tcp6_payload_used];
> -		iov[TCP_IOV_IP] =
> -			IOV_OF_LVALUE(tcp6_payload_ip[tcp6_payload_used++]);
> +		iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_payload_ip[tcp_payload_used]);
>  		iov[TCP_IOV_ETH].iov_base = &tcp6_eth_src;
> -		l4len = tcp_l2_buf_fill_headers(conn, iov, dlen, NULL, seq,
> -						false);
> -		iov[TCP_IOV_PAYLOAD].iov_len = l4len;
> -		if (tcp6_payload_used > TCP_FRAMES_MEM - 1)
> -			tcp_payload_flush(c);
>  	}
> +	l4len = tcp_l2_buf_fill_headers(conn, iov, dlen, check, seq, false);
> +	iov[TCP_IOV_PAYLOAD].iov_len = l4len;
> +	if (++tcp_payload_used > TCP_FRAMES_MEM - 1)
> +		tcp_payload_flush(c);
>  }
>  
>  /**
> @@ -388,8 +293,7 @@ int tcp_buf_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn)
>  {
>  	uint32_t wnd_scaled = conn->wnd_from_tap << conn->ws_from_tap;
>  	int fill_bufs, send_bufs = 0, last_len, iov_rem = 0;
> -	int sendlen, len, dlen, v4 = CONN_V4(conn);
> -	int s = conn->sock, i, ret = 0;
> +	int sendlen, len, dlen, i, s = conn->sock, ret = 0;
>  	struct msghdr mh_sock = { 0 };
>  	uint16_t mss = MSS_GET(conn);
>  	uint32_t already_sent, seq;
> @@ -436,19 +340,15 @@ int tcp_buf_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn)
>  		mh_sock.msg_iovlen = fill_bufs;
>  	}
>  
> -	if (( v4 && tcp4_payload_used + fill_bufs > TCP_FRAMES_MEM) ||
> -	    (!v4 && tcp6_payload_used + fill_bufs > TCP_FRAMES_MEM)) {
> +	if (tcp_payload_used + fill_bufs > TCP_FRAMES_MEM) {
>  		tcp_payload_flush(c);
>  
>  		/* Silence Coverity CWE-125 false positive */
> -		tcp4_payload_used = tcp6_payload_used = 0;
> +		tcp_payload_used = 0;
>  	}
>  
>  	for (i = 0, iov = iov_sock + 1; i < fill_bufs; i++, iov++) {
> -		if (v4)
> -			iov->iov_base = &tcp4_payload[tcp4_payload_used + i].data;
> -		else
> -			iov->iov_base = &tcp6_payload[tcp6_payload_used + i].data;
> +		iov->iov_base = &tcp_payload[tcp_payload_used + i].data;
>  		iov->iov_len = mss;
>  	}
>  	if (iov_rem)
> @@ -496,7 +396,7 @@ int tcp_buf_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn)
>  	dlen = mss;
>  	seq = conn->seq_to_tap;
>  	for (i = 0; i < send_bufs; i++) {
> -		int no_csum = i && i != send_bufs - 1 && tcp4_payload_used;
> +		int no_csum = i && i != send_bufs - 1 && tcp_payload_used;
>  
>  		if (i == send_bufs - 1)
>  			dlen = last_len;
> diff --git a/tcp_buf.h b/tcp_buf.h
> index 8d4b615..49c04d4 100644
> --- a/tcp_buf.h
> +++ b/tcp_buf.h
> @@ -6,8 +6,7 @@
>  #ifndef TCP_BUF_H
>  #define TCP_BUF_H
>  
> -void tcp_sock4_iov_init(const struct ctx *c);
> -void tcp_sock6_iov_init(const struct ctx *c);
> +void tcp_sock_iov_init(const struct ctx *c);
>  void tcp_flags_flush(const struct ctx *c);
>  void tcp_payload_flush(const struct ctx *c);
>  int tcp_buf_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn);

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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Re: [PATCH v4 0/2] tcp: unify IPv4 and IPv6 tap queues

[Stefano Brivio]

On Fri, 11 Oct 2024 14:35:38 -0400
Jon Maloy <jmaloy@redhat.com> wrote:

> This should save us some memory and code.
> 
> ---
> v2: - Setting pointers to pre-set IP and MAC headers on the fly
>       instead of copying them.
>     - Merged patch #2 and #3 from v1
> v3: - Changes based on feedback from team
> v4: - Rebased to latest version of master branch
> 
> Jon Maloy (2):
>   tcp: set ip and eth headers in l2 tap queues on the fly
>   tcp: unify l2 TCPv4 and TCPv6 queues and structures

Tests pass for me now, and, minus the pending comments from David, the
series looks good to me.

-- 
Stefano