tcp: set ip and eth headers in l2 tap queues on the fly

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>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 28 insertions, 22 deletions

diff --git a/tcp_buf.c b/tcp_buf.c
index cb6742c..e249c6b 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;
+		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[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;