[PATCH v3 1/2] hw/net: Added plen fix for IPv6

[andrew@daynix.com]

From: Andrew <andrew@daynix.com>

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1708065
With network backend with 'virtual header' - there was an issue
in 'plen' field. Overall, during TSO, 'plen' would be changed,
but with 'vheader' this field should be set to the size of the
payload itself instead of '0'.

Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
---
 hw/net/net_tx_pkt.c | 23 +++++++++++++++++++++++
 hw/net/net_tx_pkt.h | 14 ++++++++++++++
 include/net/eth.h   |  1 +
 3 files changed, 38 insertions(+)

diff --git a/hw/net/net_tx_pkt.c b/hw/net/net_tx_pkt.c
index 331c73cfc0..9560e4a49e 100644
--- a/hw/net/net_tx_pkt.c
+++ b/hw/net/net_tx_pkt.c
@@ -626,6 +626,7 @@ bool net_tx_pkt_send(struct NetTxPkt *pkt, NetClientState *nc)
 
     if (pkt->has_virt_hdr ||
         pkt->virt_hdr.gso_type == VIRTIO_NET_HDR_GSO_NONE) {
+        net_tx_pkt_fix_ip6_payload_len(pkt);
         net_tx_pkt_sendv(pkt, nc, pkt->vec,
             pkt->payload_frags + NET_TX_PKT_PL_START_FRAG);
         return true;
@@ -644,3 +645,25 @@ bool net_tx_pkt_send_loopback(struct NetTxPkt *pkt, NetClientState *nc)
 
     return res;
 }
+
+void net_tx_pkt_fix_ip6_payload_len(struct NetTxPkt *pkt)
+{
+    struct iovec *l2 = &pkt->vec[NET_TX_PKT_L2HDR_FRAG];
+    if (eth_get_l3_proto(l2, 1, l2->iov_len) == ETH_P_IPV6) {
+        struct ip6_header *ip6 = (struct ip6_header *) pkt->l3_hdr;
+        /*
+         * TODO: if qemu would support >64K packets - add jumbo option check
+         * something like that:
+         * 'if (ip6->ip6_plen == 0 && !has_jumbo_option(ip6)) {'
+         */
+        if (ip6->ip6_plen == 0) {
+            if (pkt->payload_len <= ETH_MAX_IP_DGRAM_LEN) {
+                ip6->ip6_plen = htons(pkt->payload_len);
+            }
+            /*
+             * TODO: if qemu would support >64K packets
+             * add jumbo option for packets greater then 65,535 bytes
+             */
+        }
+    }
+}
diff --git a/hw/net/net_tx_pkt.h b/hw/net/net_tx_pkt.h
index 212ecc62fc..4ec8bbe9bd 100644
--- a/hw/net/net_tx_pkt.h
+++ b/hw/net/net_tx_pkt.h
@@ -187,4 +187,18 @@ bool net_tx_pkt_parse(struct NetTxPkt *pkt);
 */
 bool net_tx_pkt_has_fragments(struct NetTxPkt *pkt);
 
+/**
+ * Fix IPv6 'plen' field.
+ * If ipv6 payload length field is 0 - then there should be Hop-by-Hop
+ * option for packets greater than 65,535.
+ * For packets with a payload less than 65,535: fix 'plen' field.
+ * For backends with vheader, we need just one packet with proper
+ * payload size. For now, qemu drops every packet with size greater 64K
+ * (see net_tx_pkt_send()) so, there is no reason to add jumbo option to ip6
+ * hop-by-hop extension if it's missed
+ *
+ * @pkt            packet
+ */
+void net_tx_pkt_fix_ip6_payload_len(struct NetTxPkt *pkt);
+
 #endif
diff --git a/include/net/eth.h b/include/net/eth.h
index 7f45c678e7..0671be6916 100644
--- a/include/net/eth.h
+++ b/include/net/eth.h
@@ -186,6 +186,7 @@ struct tcp_hdr {
 
 #define ip6_nxt      ip6_ctlun.ip6_un1.ip6_un1_nxt
 #define ip6_ecn_acc  ip6_ctlun.ip6_un3.ip6_un3_ecn
+#define ip6_plen     ip6_ctlun.ip6_un1.ip6_un1_plen
 
 #define PKT_GET_ETH_HDR(p)        \
     ((struct eth_header *)(p))
-- 
2.27.0