hw/net/net_tx_pkt: Implement TCP segmentation

There was no proper implementation of TCP segmentation before this
change, and net_tx_pkt relied solely on IPv4 fragmentation. Not only
this is not aligned with the specification, but it also resulted in
corrupted IPv6 packets.

This is particularly problematic for the igb, a new proposed device
implementation; igb provides loopback feature for VMDq and the feature
relies on software segmentation.

Implement proper TCP segmentation in net_tx_pkt to fix such a scenario.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

hw/net/net_tx_pkt.c

@@ -326,7 +326,8 @@ bool net_tx_pkt_build_vheader(struct NetTxPkt *pkt, bool tso_enable,
     case VIRTIO_NET_HDR_GSO_TCPV6:
         bytes_read = iov_to_buf(&pkt->vec[NET_TX_PKT_PL_START_FRAG],
                                 pkt->payload_frags, 0, &l4hdr, sizeof(l4hdr));
-        if (bytes_read < sizeof(l4hdr)) {
+        if (bytes_read < sizeof(l4hdr) ||
+            l4hdr.th_off * sizeof(uint32_t) < sizeof(l4hdr)) {
             return false;
         }
 
@@ -466,15 +467,14 @@ void net_tx_pkt_reset(struct NetTxPkt *pkt)
     pkt->l4proto = 0;
 }
 
-static void net_tx_pkt_do_sw_csum(struct NetTxPkt *pkt)
+static void net_tx_pkt_do_sw_csum(struct NetTxPkt *pkt,
+                                  struct iovec *iov, uint32_t iov_len,
+                                  uint16_t csl)
 {
-    struct iovec *iov = &pkt->vec[NET_TX_PKT_L2HDR_FRAG];
     uint32_t csum_cntr;
     uint16_t csum = 0;
     uint32_t cso;
     /* num of iovec without vhdr */
-    uint32_t iov_len = pkt->payload_frags + NET_TX_PKT_PL_START_FRAG - 1;
-    uint16_t csl;
     size_t csum_offset = pkt->virt_hdr.csum_start + pkt->virt_hdr.csum_offset;
     uint16_t l3_proto = eth_get_l3_proto(iov, 1, iov->iov_len);
 
@@ -482,8 +482,6 @@ static void net_tx_pkt_do_sw_csum(struct NetTxPkt *pkt)
     iov_from_buf(iov, iov_len, csum_offset, &csum, sizeof csum);
 
     /* Calculate L4 TCP/UDP checksum */
-    csl = pkt->payload_len;
-
     csum_cntr = 0;
     cso = 0;
     /* add pseudo header to csum */
@@ -509,14 +507,13 @@ static void net_tx_pkt_do_sw_csum(struct NetTxPkt *pkt)
 #define NET_MAX_FRAG_SG_LIST (64)
 
 static size_t net_tx_pkt_fetch_fragment(struct NetTxPkt *pkt,
-    int *src_idx, size_t *src_offset, struct iovec *dst, int *dst_idx)
+    int *src_idx, size_t *src_offset, size_t src_len,
+    struct iovec *dst, int *dst_idx)
 {
     size_t fetched = 0;
     struct iovec *src = pkt->vec;
 
-    *dst_idx = NET_TX_PKT_PL_START_FRAG;
+    while (fetched < src_len) {
-
-    while (fetched < IP_FRAG_ALIGN_SIZE(pkt->virt_hdr.gso_size)) {
 
         /* no more place in fragment iov */
         if (*dst_idx == NET_MAX_FRAG_SG_LIST) {
@@ -531,7 +528,7 @@ static size_t net_tx_pkt_fetch_fragment(struct NetTxPkt *pkt,
 
         dst[*dst_idx].iov_base = src[*src_idx].iov_base + *src_offset;
         dst[*dst_idx].iov_len = MIN(src[*src_idx].iov_len - *src_offset,
-            IP_FRAG_ALIGN_SIZE(pkt->virt_hdr.gso_size) - fetched);
+            src_len - fetched);
 
         *src_offset += dst[*dst_idx].iov_len;
         fetched += dst[*dst_idx].iov_len;
@@ -560,58 +557,223 @@ static void net_tx_pkt_sendv(
     }
 }
 
+static bool net_tx_pkt_tcp_fragment_init(struct NetTxPkt *pkt,
+                                         struct iovec *fragment,
+                                         int *pl_idx,
+                                         size_t *l4hdr_len,
+                                         int *src_idx,
+                                         size_t *src_offset,
+                                         size_t *src_len)
+{
+    struct iovec *l4 = fragment + NET_TX_PKT_PL_START_FRAG;
+    size_t bytes_read = 0;
+    struct tcp_hdr *th;
+
+    if (!pkt->payload_frags) {
+        return false;
+    }
+
+    l4->iov_len = pkt->virt_hdr.hdr_len - pkt->hdr_len;
+    l4->iov_base = g_malloc(l4->iov_len);
+
+    *src_idx = NET_TX_PKT_PL_START_FRAG;
+    while (pkt->vec[*src_idx].iov_len < l4->iov_len - bytes_read) {
+        memcpy((char *)l4->iov_base + bytes_read, pkt->vec[*src_idx].iov_base,
+               pkt->vec[*src_idx].iov_len);
+
+        bytes_read += pkt->vec[*src_idx].iov_len;
+
+        (*src_idx)++;
+        if (*src_idx >= pkt->payload_frags + NET_TX_PKT_PL_START_FRAG) {
+            g_free(l4->iov_base);
+            return false;
+        }
+    }
+
+    *src_offset = l4->iov_len - bytes_read;
+    memcpy((char *)l4->iov_base + bytes_read, pkt->vec[*src_idx].iov_base,
+           *src_offset);
+
+    th = l4->iov_base;
+    th->th_flags &= ~(TH_FIN | TH_PUSH);
+
+    *pl_idx = NET_TX_PKT_PL_START_FRAG + 1;
+    *l4hdr_len = l4->iov_len;
+    *src_len = pkt->virt_hdr.gso_size;
+
+    return true;
+}
+
+static void net_tx_pkt_tcp_fragment_deinit(struct iovec *fragment)
+{
+    g_free(fragment[NET_TX_PKT_PL_START_FRAG].iov_base);
+}
+
+static void net_tx_pkt_tcp_fragment_fix(struct NetTxPkt *pkt,
+                                        struct iovec *fragment,
+                                        size_t fragment_len,
+                                        uint8_t gso_type)
+{
+    struct iovec *l3hdr = fragment + NET_TX_PKT_L3HDR_FRAG;
+    struct iovec *l4hdr = fragment + NET_TX_PKT_PL_START_FRAG;
+    struct ip_header *ip = l3hdr->iov_base;
+    struct ip6_header *ip6 = l3hdr->iov_base;
+    size_t len = l3hdr->iov_len + l4hdr->iov_len + fragment_len;
+
+    switch (gso_type) {
+    case VIRTIO_NET_HDR_GSO_TCPV4:
+        ip->ip_len = cpu_to_be16(len);
+        eth_fix_ip4_checksum(l3hdr->iov_base, l3hdr->iov_len);
+        break;
+
+    case VIRTIO_NET_HDR_GSO_TCPV6:
+        len -= sizeof(struct ip6_header);
+        ip6->ip6_ctlun.ip6_un1.ip6_un1_plen = cpu_to_be16(len);
+        break;
+    }
+}
+
+static void net_tx_pkt_tcp_fragment_advance(struct NetTxPkt *pkt,
+                                            struct iovec *fragment,
+                                            size_t fragment_len,
+                                            uint8_t gso_type)
+{
+    struct iovec *l3hdr = fragment + NET_TX_PKT_L3HDR_FRAG;
+    struct iovec *l4hdr = fragment + NET_TX_PKT_PL_START_FRAG;
+    struct ip_header *ip = l3hdr->iov_base;
+    struct tcp_hdr *th = l4hdr->iov_base;
+
+    if (gso_type == VIRTIO_NET_HDR_GSO_TCPV4) {
+        ip->ip_id = cpu_to_be16(be16_to_cpu(ip->ip_id) + 1);
+    }
+
+    th->th_seq = cpu_to_be32(be32_to_cpu(th->th_seq) + fragment_len);
+    th->th_flags &= ~TH_CWR;
+}
+
+static void net_tx_pkt_udp_fragment_init(struct NetTxPkt *pkt,
+                                         int *pl_idx,
+                                         size_t *l4hdr_len,
+                                         int *src_idx, size_t *src_offset,
+                                         size_t *src_len)
+{
+    *pl_idx = NET_TX_PKT_PL_START_FRAG;
+    *l4hdr_len = 0;
+    *src_idx = NET_TX_PKT_PL_START_FRAG;
+    *src_offset = 0;
+    *src_len = IP_FRAG_ALIGN_SIZE(pkt->virt_hdr.gso_size);
+}
+
+static void net_tx_pkt_udp_fragment_fix(struct NetTxPkt *pkt,
+                                        struct iovec *fragment,
+                                        size_t fragment_offset,
+                                        size_t fragment_len)
+{
+    bool more_frags = fragment_offset + fragment_len < pkt->payload_len;
+    uint16_t orig_flags;
+    struct iovec *l3hdr = fragment + NET_TX_PKT_L3HDR_FRAG;
+    struct ip_header *ip = l3hdr->iov_base;
+    uint16_t frag_off_units = fragment_offset / IP_FRAG_UNIT_SIZE;
+    uint16_t new_ip_off;
+
+    assert(fragment_offset % IP_FRAG_UNIT_SIZE == 0);
+    assert((frag_off_units & ~IP_OFFMASK) == 0);
+
+    orig_flags = be16_to_cpu(ip->ip_off) & ~(IP_OFFMASK | IP_MF);
+    new_ip_off = frag_off_units | orig_flags | (more_frags ? IP_MF : 0);
+    ip->ip_off = cpu_to_be16(new_ip_off);
+    ip->ip_len = cpu_to_be16(l3hdr->iov_len + fragment_len);
+
+    eth_fix_ip4_checksum(l3hdr->iov_base, l3hdr->iov_len);
+}
+
 static bool net_tx_pkt_do_sw_fragmentation(struct NetTxPkt *pkt,
                                            NetTxPktCallback callback,
                                            void *context)
 {
-    struct iovec fragment[NET_MAX_FRAG_SG_LIST];
+    uint8_t gso_type = pkt->virt_hdr.gso_type & ~VIRTIO_NET_HDR_GSO_ECN;
-    size_t fragment_len = 0;
-    bool more_frags = false;
 
-    /* some pointers for shorter code */
+    struct iovec fragment[NET_MAX_FRAG_SG_LIST];
-    void *l2_iov_base, *l3_iov_base;
+    size_t fragment_len;
-    size_t l2_iov_len, l3_iov_len;
+    size_t l4hdr_len;
-    int src_idx =  NET_TX_PKT_PL_START_FRAG, dst_idx;
+    size_t src_len;
-    size_t src_offset = 0;
+
+    int src_idx, dst_idx, pl_idx;
+    size_t src_offset;
     size_t fragment_offset = 0;
     struct virtio_net_hdr virt_hdr = {
         .flags = pkt->virt_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM ?
                  VIRTIO_NET_HDR_F_DATA_VALID : 0
     };
 
-    l2_iov_base = pkt->vec[NET_TX_PKT_L2HDR_FRAG].iov_base;
-    l2_iov_len = pkt->vec[NET_TX_PKT_L2HDR_FRAG].iov_len;
-    l3_iov_base = pkt->vec[NET_TX_PKT_L3HDR_FRAG].iov_base;
-    l3_iov_len = pkt->vec[NET_TX_PKT_L3HDR_FRAG].iov_len;
-
     /* Copy headers */
     fragment[NET_TX_PKT_VHDR_FRAG].iov_base = &virt_hdr;
     fragment[NET_TX_PKT_VHDR_FRAG].iov_len = sizeof(virt_hdr);
-    fragment[NET_TX_PKT_L2HDR_FRAG].iov_base = l2_iov_base;
+    fragment[NET_TX_PKT_L2HDR_FRAG] = pkt->vec[NET_TX_PKT_L2HDR_FRAG];
-    fragment[NET_TX_PKT_L2HDR_FRAG].iov_len = l2_iov_len;
+    fragment[NET_TX_PKT_L3HDR_FRAG] = pkt->vec[NET_TX_PKT_L3HDR_FRAG];
-    fragment[NET_TX_PKT_L3HDR_FRAG].iov_base = l3_iov_base;
-    fragment[NET_TX_PKT_L3HDR_FRAG].iov_len = l3_iov_len;
 
+    switch (gso_type) {
+    case VIRTIO_NET_HDR_GSO_TCPV4:
+    case VIRTIO_NET_HDR_GSO_TCPV6:
+        if (!net_tx_pkt_tcp_fragment_init(pkt, fragment, &pl_idx, &l4hdr_len,
+                                          &src_idx, &src_offset, &src_len)) {
+            return false;
+        }
+        break;
+
+    case VIRTIO_NET_HDR_GSO_UDP:
+        net_tx_pkt_do_sw_csum(pkt, &pkt->vec[NET_TX_PKT_L2HDR_FRAG],
+                              pkt->payload_frags + NET_TX_PKT_PL_START_FRAG - 1,
+                              pkt->payload_len);
+        net_tx_pkt_udp_fragment_init(pkt, &pl_idx, &l4hdr_len,
+                                     &src_idx, &src_offset, &src_len);
+        break;
+
+    default:
+        abort();
+    }
 
     /* Put as much data as possible and send */
-    do {
+    while (true) {
-        fragment_len = net_tx_pkt_fetch_fragment(pkt, &src_idx, &src_offset,
+        dst_idx = pl_idx;
-            fragment, &dst_idx);
+        fragment_len = net_tx_pkt_fetch_fragment(pkt,
+            &src_idx, &src_offset, src_len, fragment, &dst_idx);
+        if (!fragment_len) {
+            break;
+        }
 
-        more_frags = (fragment_offset + fragment_len < pkt->payload_len);
+        switch (gso_type) {
+        case VIRTIO_NET_HDR_GSO_TCPV4:
+        case VIRTIO_NET_HDR_GSO_TCPV6:
+            net_tx_pkt_tcp_fragment_fix(pkt, fragment, fragment_len, gso_type);
+            net_tx_pkt_do_sw_csum(pkt, fragment + NET_TX_PKT_L2HDR_FRAG,
+                                  dst_idx - NET_TX_PKT_L2HDR_FRAG,
+                                  l4hdr_len + fragment_len);
+            break;
 
-        eth_setup_ip4_fragmentation(l2_iov_base, l2_iov_len, l3_iov_base,
+        case VIRTIO_NET_HDR_GSO_UDP:
-            l3_iov_len, fragment_len, fragment_offset, more_frags);
+            net_tx_pkt_udp_fragment_fix(pkt, fragment, fragment_offset,
-
+                                        fragment_len);
-        eth_fix_ip4_checksum(l3_iov_base, l3_iov_len);
+            break;
+        }
 
         callback(context,
                  fragment + NET_TX_PKT_L2HDR_FRAG, dst_idx - NET_TX_PKT_L2HDR_FRAG,
                  fragment + NET_TX_PKT_VHDR_FRAG, dst_idx - NET_TX_PKT_VHDR_FRAG);
 
-        fragment_offset += fragment_len;
+        if (gso_type == VIRTIO_NET_HDR_GSO_TCPV4 ||
+            gso_type == VIRTIO_NET_HDR_GSO_TCPV6) {
+            net_tx_pkt_tcp_fragment_advance(pkt, fragment, fragment_len,
+                                            gso_type);
+        }
 
-    } while (fragment_len && more_frags);
+        fragment_offset += fragment_len;
+    }
+
+    if (gso_type == VIRTIO_NET_HDR_GSO_TCPV4 ||
+        gso_type == VIRTIO_NET_HDR_GSO_TCPV6) {
+        net_tx_pkt_tcp_fragment_deinit(fragment);
+    }
 
     return true;
 }
@@ -627,10 +789,6 @@ bool net_tx_pkt_send_custom(struct NetTxPkt *pkt, bool offload,
 {
     assert(pkt);
 
-    if (!offload && pkt->virt_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
-        net_tx_pkt_do_sw_csum(pkt);
-    }
-
     /*
      * Since underlying infrastructure does not support IP datagrams longer
      * than 64K we should drop such packets and don't even try to send
@@ -644,6 +802,12 @@ bool net_tx_pkt_send_custom(struct NetTxPkt *pkt, bool offload,
     }
 
     if (offload || pkt->virt_hdr.gso_type == VIRTIO_NET_HDR_GSO_NONE) {
+        if (!offload && pkt->virt_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
+            net_tx_pkt_do_sw_csum(pkt, &pkt->vec[NET_TX_PKT_L2HDR_FRAG],
+                                  pkt->payload_frags + NET_TX_PKT_PL_START_FRAG - 1,
+                                  pkt->payload_len);
+        }
+
         net_tx_pkt_fix_ip6_payload_len(pkt);
         callback(context, pkt->vec + NET_TX_PKT_L2HDR_FRAG,
                  pkt->payload_frags + NET_TX_PKT_PL_START_FRAG - NET_TX_PKT_L2HDR_FRAG,

include/net/eth.h

@@ -400,11 +400,6 @@ void eth_get_protocols(const struct iovec *iov, int iovcnt,
                        eth_ip4_hdr_info *ip4hdr_info,
                        eth_l4_hdr_info  *l4hdr_info);
 
-void eth_setup_ip4_fragmentation(const void *l2hdr, size_t l2hdr_len,
-                                 void *l3hdr, size_t l3hdr_len,
-                                 size_t l3payload_len,
-                                 size_t frag_offset, bool more_frags);
-
 void
 eth_fix_ip4_checksum(void *l3hdr, size_t l3hdr_len);
 

net/eth.c

@@ -314,33 +314,6 @@ eth_strip_vlan_ex(const struct iovec *iov, int iovcnt, size_t iovoff,
     return 0;
 }
 
-void
-eth_setup_ip4_fragmentation(const void *l2hdr, size_t l2hdr_len,
-                            void *l3hdr, size_t l3hdr_len,
-                            size_t l3payload_len,
-                            size_t frag_offset, bool more_frags)
-{
-    const struct iovec l2vec = {
-        .iov_base = (void *) l2hdr,
-        .iov_len = l2hdr_len
-    };
-
-    if (eth_get_l3_proto(&l2vec, 1, l2hdr_len) == ETH_P_IP) {
-        uint16_t orig_flags;
-        struct ip_header *iphdr = (struct ip_header *) l3hdr;
-        uint16_t frag_off_units = frag_offset / IP_FRAG_UNIT_SIZE;
-        uint16_t new_ip_off;
-
-        assert(frag_offset % IP_FRAG_UNIT_SIZE == 0);
-        assert((frag_off_units & ~IP_OFFMASK) == 0);
-
-        orig_flags = be16_to_cpu(iphdr->ip_off) & ~(IP_OFFMASK|IP_MF);
-        new_ip_off = frag_off_units | orig_flags  | (more_frags ? IP_MF : 0);
-        iphdr->ip_off = cpu_to_be16(new_ip_off);
-        iphdr->ip_len = cpu_to_be16(l3payload_len + l3hdr_len);
-    }
-}
-
 void
 eth_fix_ip4_checksum(void *l3hdr, size_t l3hdr_len)
 {