[Qemu-devel] [PATCH v6 2/3] rtl8139: add vlan tag extraction

[Jason Wang]

Benjamin Poirier writes:
 > Add support to the emulated hardware to extract vlan tags in packets
 > going from the network to the guest.
 > 
 > Signed-off-by: Benjamin Poirier <address@hidden>
 > Cc: Igor V. Kovalenko <address@hidden>
 > Cc: Jason Wang <address@hidden>
 > Cc: Michael S. Tsirkin <address@hidden>
 > Cc: Blue Swirl <address@hidden>
 > 

This patch looks functionally right, and one thing needed to be considered is
the dot1q_buf optimization for TX loopback (which is rerely used I think). I
notice it would bring extra complexity for both crc and padding. Maybe we could
just add the vlan tag in tx and pass a whole buffer to rx (Though it may bring
one more copy, but it could greatly simplifized the code).

Any thoughts?

 > --
 > 
 > AFAIK, extraction is optional to get vlans working. The driver
 > requests rx detagging but should not assume that it was done. Under
 > Linux, the mac layer will catch the vlan ethertype. I only added this
 > part for completeness (to emulate the hardware more truthfully...)
 > ---
 >  hw/rtl8139.c |  125 
 > ++++++++++++++++++++++++++++++++++++++++++++++++++--------
 >  1 files changed, 108 insertions(+), 17 deletions(-)
 > 
 > diff --git a/hw/rtl8139.c b/hw/rtl8139.c
 > index 3772ac1..312d362 100644
 > --- a/hw/rtl8139.c
 > +++ b/hw/rtl8139.c
 > @@ -72,6 +72,22 @@
 >  #define MOD2(input, size) \
 >      ( ( input ) & ( size - 1 )  )
 >  
 > +#define min(x, y) ({                \
 > +    typeof(x) _min1 = (x);          \
 > +    typeof(y) _min2 = (y);          \
 > +    (void) (&_min1 == &_min2);      \
 > +    _min1 < _min2 ? _min1 : _min2; })
 > +
 > +#define ETHER_ADDR_LEN 6
 > +#define ETHER_TYPE_LEN 2
 > +#define ETH_HLEN (ETHER_ADDR_LEN * 2 + ETHER_TYPE_LEN)
 > +#define ETH_P_IP    0x0800      /* Internet Protocol packet */
 > +#define ETH_P_8021Q 0x8100      /* 802.1Q VLAN Extended Header  */
 > +#define ETH_MTU     1500
 > +
 > +#define VLAN_TCI_LEN 2
 > +#define VLAN_HLEN (ETHER_TYPE_LEN + VLAN_TCI_LEN)
 > +
 >  #if defined (DEBUG_RTL8139)
 >  #  define DEBUG_PRINT(x) do { printf x ; } while (0)
 >  #else
 > @@ -777,6 +793,14 @@ static void rtl8139_write_buffer(RTL8139State *s, const 
 > void *buf, int size)
 >      s->RxBufAddr += size;
 >  }
 >  
 > +static unsigned long rtl8139_write_buffer_crc(RTL8139State *s, const void
 > +    *buf, int size, unsigned long crc)
 > +{
 > +    rtl8139_write_buffer(s, buf, size);
 > +    return crc32(crc, buf, size);
 > +}
 > +
 > +
 >  #define MIN_BUF_SIZE 60
 >  static inline target_phys_addr_t rtl8139_addr64(uint32_t low, uint32_t high)
 >  {
 > @@ -809,14 +833,20 @@ static int rtl8139_can_receive(VLANClientState *nc)
 >      }
 >  }
 >  
 > -static ssize_t rtl8139_do_receive(VLANClientState *nc, const uint8_t *buf, 
 > size_t size_, int do_interrupt)
 > +static ssize_t rtl8139_do_receive(VLANClientState *nc, const uint8_t *buf,
 > +    size_t buf_size, int do_interrupt, const uint8_t *dot1q_buf)
 >  {
 >      RTL8139State *s = DO_UPCAST(NICState, nc, nc)->opaque;
 > +    /* size_ is the total length of argument buffers */
 > +    const int size_ = buf_size + (dot1q_buf ? VLAN_HLEN : 0);
 > +    /* size is the length of the buffer passed to the driver */
 >      int size = size_;
 > +    const uint8_t *next_part;
 > +    size_t next_part_size;
 >  
 >      uint32_t packet_header = 0;
 >  
 > -    uint8_t buf1[60];
 > +    uint8_t buf1[MIN_BUF_SIZE];
 >      static const uint8_t broadcast_macaddr[6] =
 >          { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
 >  
 > @@ -930,10 +960,28 @@ static ssize_t rtl8139_do_receive(VLANClientState *nc, 
 > const uint8_t *buf, size_
 >  
 >      /* if too small buffer, then expand it */
 >      if (size < MIN_BUF_SIZE) {
 > -        memcpy(buf1, buf, size);
 > -        memset(buf1 + size, 0, MIN_BUF_SIZE - size);
 > +        size_t copied_size;
 > +
 > +        copied_size = min((size_t) ETHER_ADDR_LEN * 2, buf_size);
 > +        memcpy(buf1, buf, copied_size);
 > +        buf_size -= copied_size;
 > +
 > +        if (dot1q_buf) {
 > +            if (copied_size >= ETHER_ADDR_LEN * 2) {
 > +                memcpy(buf1 + copied_size, dot1q_buf, VLAN_HLEN);
 > +                copied_size += VLAN_HLEN;
 > +            }
 > +            dot1q_buf = NULL;
 > +        }
 > +
 > +        if (buf_size > 0) {
 > +            memcpy(buf1 + copied_size, &buf[ETHER_ADDR_LEN * 2], buf_size);
 > +            copied_size += buf_size;
 > +        }
 > +        memset(buf1 + copied_size, 0, MIN_BUF_SIZE - copied_size);
 >          buf = buf1;
 >          size = MIN_BUF_SIZE;
 > +        buf_size = MIN_BUF_SIZE;
 >      }
 >  
 >      if (rtl8139_cp_receiver_enabled(s))
 > @@ -996,6 +1044,37 @@ static ssize_t rtl8139_do_receive(VLANClientState *nc, 
 > const uint8_t *buf, size_
 >  
 >          uint32_t rx_space = rxdw0 & CP_RX_BUFFER_SIZE_MASK;
 >  
 > +        /* write VLAN info to descriptor variables.
 > +         * The "logical" packet is formed of:
 > +         * * buf[0..12[,
 > +         * * dot1q_buf (if offloading is enabled and tag is present or
 > +         *   dot1q_buf is passed in argument),
 > +         * * next_part[0..next_part_size[.
 > +         */
 > +        next_part = &buf[ETHER_ADDR_LEN * 2];
 > +        if (s->CpCmd & CPlusRxVLAN && (dot1q_buf || be16_to_cpup((uint16_t 
 > *)
 > +                    next_part) == ETH_P_8021Q)) {
 > +            if (!dot1q_buf) {
 > +                /* the tag is in the buffer */
 > +                dot1q_buf = next_part;
 > +                next_part += VLAN_HLEN;
 > +            }
 > +            size -= VLAN_HLEN;
 > +
 > +            rxdw1 &= ~CP_RX_VLAN_TAG_MASK;
 > +            /* BE + ~le_to_cpu()~ + cpu_to_le() = BE */
 > +            rxdw1 |= CP_RX_TAVA | le16_to_cpup((uint16_t *)
 > +                &dot1q_buf[ETHER_TYPE_LEN]);
 > +
 > +            DEBUG_PRINT(("RTL8139: C+ Rx mode : extracted vlan tag with 
 > tci: "
 > +                    "%u\n", be16_to_cpup((uint16_t *)
 > +                        &dot1q_buf[ETHER_TYPE_LEN])));
 > +        } else {
 > +            /* reset VLAN tag flag */
 > +            rxdw1 &= ~CP_RX_TAVA;
 > +        }
 > +        next_part_size = buf + buf_size - next_part;
 > +
 >          /* TODO: scatter the packet over available receive ring descriptors 
 > space */
 >  
 >          if (size+4 > rx_space)
 > @@ -1017,7 +1096,18 @@ static ssize_t rtl8139_do_receive(VLANClientState 
 > *nc, const uint8_t *buf, size_
 >          target_phys_addr_t rx_addr = rtl8139_addr64(rxbufLO, rxbufHI);
 >  
 >          /* receive/copy to target memory */
 > -        cpu_physical_memory_write( rx_addr, buf, size );
 > +        cpu_physical_memory_write(rx_addr, buf, 2 * ETHER_ADDR_LEN);
 > +        val = crc32(0, buf, 2 * ETHER_ADDR_LEN);
 > +        if (dot1q_buf) {
 > +            if (!(s->CpCmd & CPlusRxVLAN)) {
 > +                cpu_physical_memory_write(rx_addr + 2 * ETHER_ADDR_LEN,
 > +                    dot1q_buf, VLAN_HLEN);
 > +            }
 > +            val = crc32(val, dot1q_buf, VLAN_HLEN);
 > +        }
 > +        cpu_physical_memory_write(rx_addr + size - next_part_size, 
 > next_part,
 > +            next_part_size);
 > +        val = crc32(val, next_part, next_part_size);
 >  
 >          if (s->CpCmd & CPlusRxChkSum)
 >          {
 > @@ -1025,7 +1115,7 @@ static ssize_t rtl8139_do_receive(VLANClientState *nc, 
 > const uint8_t *buf, size_
 >          }
 >  
 >          /* write checksum */
 > -        val = cpu_to_le32(crc32(0, buf, size));
 > +        val = cpu_to_le32(val);
 >          cpu_physical_memory_write( rx_addr+size, (uint8_t *)&val, 4);
 >  
 >  /* first segment of received packet flag */
 > @@ -1070,9 +1160,6 @@ static ssize_t rtl8139_do_receive(VLANClientState *nc, 
 > const uint8_t *buf, size_
 >          rxdw0 &= ~CP_RX_BUFFER_SIZE_MASK;
 >          rxdw0 |= (size+4);
 >  
 > -        /* reset VLAN tag flag */
 > -        rxdw1 &= ~CP_RX_TAVA;
 > -
 >          /* update ring data */
 >          val = cpu_to_le32(rxdw0);
 >          cpu_physical_memory_write(cplus_rx_ring_desc,    (uint8_t *)&val, 
 > 4);
 > @@ -1124,10 +1211,18 @@ static ssize_t rtl8139_do_receive(VLANClientState 
 > *nc, const uint8_t *buf, size_
 >  
 >          rtl8139_write_buffer(s, (uint8_t *)&val, 4);
 >  
 > -        rtl8139_write_buffer(s, buf, size);
 > +        /* receive/copy to target memory */
 > +        if (dot1q_buf) {
 > +            val = rtl8139_write_buffer_crc(s, buf, 2 * ETHER_ADDR_LEN, 0);
 > +            val = rtl8139_write_buffer_crc(s, dot1q_buf, VLAN_HLEN, val);
 > +            val = rtl8139_write_buffer_crc(s, buf + 2 * ETHER_ADDR_LEN,
 > +                buf_size - 2 * ETHER_ADDR_LEN, val);
 > +        } else {
 > +            val = rtl8139_write_buffer_crc(s, buf, size, 0);
 > +        }
 >  
 >          /* write checksum */
 > -        val = cpu_to_le32(crc32(0, buf, size));
 > +        val = cpu_to_le32(val);
 >          rtl8139_write_buffer(s, (uint8_t *)&val, 4);
 >  
 >          /* correct buffer write pointer */
 > @@ -1151,7 +1246,7 @@ static ssize_t rtl8139_do_receive(VLANClientState *nc, 
 > const uint8_t *buf, size_
 >  
 >  static ssize_t rtl8139_receive(VLANClientState *nc, const uint8_t *buf, 
 > size_t size)
 >  {
 > -    return rtl8139_do_receive(nc, buf, size, 1);
 > +    return rtl8139_do_receive(nc, buf, size, 1, NULL);
 >  }
 >  
 >  static void rtl8139_reset_rxring(RTL8139State *s, uint32_t bufferSize)
 > @@ -1737,7 +1832,7 @@ static void rtl8139_transfer_frame(RTL8139State *s, 
 > const uint8_t *buf, int size
 >      if (TxLoopBack == (s->TxConfig & TxLoopBack))
 >      {
 >          DEBUG_PRINT(("RTL8139: +++ transmit loopback mode\n"));
 > -        rtl8139_do_receive(&s->nic->nc, buf, size, do_interrupt);
 > +        rtl8139_do_receive(&s->nic->nc, buf, size, do_interrupt, NULL);
 >      }
 >      else
 >      {
 > @@ -2066,10 +2161,6 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s)
 >          {
 >              DEBUG_PRINT(("RTL8139: +++ C+ mode offloaded task checksum\n"));
 >  
 > -            #define ETH_P_IP        0x0800          /* Internet Protocol 
 > packet     */
 > -            #define ETH_HLEN    14
 > -            #define ETH_MTU     1500
 > -
 >              /* ip packet header */
 >              ip_header *ip = NULL;
 >              int hlen = 0;
 > -- 
 > 1.7.2.3
 >