Re: [Qemu-devel] [PATCH v2 1/2] rtl8139: add vlan tag insertion

[Benjamin Poirier <benjamin.poirier@polymtl.ca>]

On 16/11/10 03:06 PM, Anthony Liguori wrote:
> On 11/08/2010 07:46 PM, Benjamin Poirier wrote:
>> Add support to the emulated hardware to add vlan tags in packets going
>> from the guest to the network.
>>
>> Signed-off-by: Benjamin Poirier<benjamin.poirier@polymtl.ca>
>> Cc: Igor V. Kovalenko<igor.v.kovalenko@gmail.com>
>> ---
>> Changes since v1:
>> * moved the debug print statement inside the if block and reworded
>>    accordingly. (as suggested by Igor)
>>
>>   hw/rtl8139.c |   45 ++++++++++++++++++++++++++++++++++-----------
>>   1 files changed, 34 insertions(+), 11 deletions(-)
>>
>> diff --git a/hw/rtl8139.c b/hw/rtl8139.c
>> index d92981d..b599945 100644
>> --- a/hw/rtl8139.c
>> +++ b/hw/rtl8139.c
>> @@ -47,6 +47,8 @@
>>    *                                  Darwin)
>>    */
>>
>> +#include<net/ethernet.h>
>> +
>>   #include "hw.h"
>>   #include "pci.h"
>>   #include "qemu-timer.h"
>> @@ -58,6 +60,10 @@
>>
>>   #define PCI_FREQUENCY 33000000L
>>
>> +/* bytes in VLAN tag */
>> +#define VLAN_TCI_LEN 2
>> +#define VLAN_HDR_LEN (ETHER_TYPE_LEN + VLAN_TCI_LEN)
>> +
>>   /* debug RTL8139 card C+ mode only */
>>   //#define DEBUG_RTL8139CP 1
>>
>> @@ -1913,7 +1919,6 @@ static int
>> rtl8139_cplus_transmit_one(RTL8139State *s)
>>
>>       cpu_physical_memory_read(cplus_tx_ring_desc,    (uint8_t *)&val,
>> 4);
>>       txdw0 = le32_to_cpu(val);
>> -    /* TODO: implement VLAN tagging support, VLAN tag data is read to
>> txdw1 */
>>       cpu_physical_memory_read(cplus_tx_ring_desc+4,  (uint8_t *)&val,
>> 4);
>>       txdw1 = le32_to_cpu(val);
>>       cpu_physical_memory_read(cplus_tx_ring_desc+8,  (uint8_t *)&val,
>> 4);
>> @@ -1925,9 +1930,6 @@ static int
>> rtl8139_cplus_transmit_one(RTL8139State *s)
>>              descriptor,
>>              txdw0, txdw1, txbufLO, txbufHI));
>>
>> -    /* TODO: the following discard cast should clean clang analyzer
>> output */
>> -    (void)txdw1;
>> -
>>   /* w0 ownership flag */
>>   #define CP_TX_OWN (1<<31)
>>   /* w0 end of ring flag */
>> @@ -1951,8 +1953,8 @@ static int
>> rtl8139_cplus_transmit_one(RTL8139State *s)
>>   /* w0 bits 0...15 : buffer size */
>>   #define CP_TX_BUFFER_SIZE (1<<16)
>>   #define CP_TX_BUFFER_SIZE_MASK (CP_TX_BUFFER_SIZE - 1)
>> -/* w1 tag available flag */
>> -#define CP_RX_TAGC (1<<17)
>> +/* w1 add tag flag */
>> +#define CP_TX_TAGC (1<<17)
>>   /* w1 bits 0...15 : VLAN tag */
>>   #define CP_TX_VLAN_TAG_MASK ((1<<16) - 1)
>>   /* w2 low  32bit of Rx buffer ptr */
>> @@ -1978,12 +1980,21 @@ static int
>> rtl8139_cplus_transmit_one(RTL8139State *s)
>>
>>       DEBUG_PRINT(("RTL8139: +++ C+ Tx mode : transmitting from
>> descriptor %d\n", descriptor));
>>
>> +    int vlan_extra_size = 0;
>>       if (txdw0&  CP_TX_FS)
>>       {
>>           DEBUG_PRINT(("RTL8139: +++ C+ Tx mode : descriptor %d is
>> first segment descriptor\n", descriptor));
>>
>>           /* reset internal buffer offset */
>>           s->cplus_txbuffer_offset = 0;
>> +
>> +        if (txdw1&  CP_TX_TAGC)
>> +        {
>> +            vlan_extra_size = VLAN_HDR_LEN;
>> +
>> +            DEBUG_PRINT(("RTL8139: +++ C+ Tx mode : inserting vlan
>> tag with "
>> +                    "tci: %u\n", bswap16(txdw1&  CP_TX_VLAN_TAG_MASK)));
>> +        }
>>       }
>>
>>       int txsize = txdw0&  CP_TX_BUFFER_SIZE_MASK;
>> @@ -1992,14 +2003,15 @@ static int
>> rtl8139_cplus_transmit_one(RTL8139State *s)
>>       /* make sure we have enough space to assemble the packet */
>>       if (!s->cplus_txbuffer)
>>       {
>> -        s->cplus_txbuffer_len = CP_TX_BUFFER_SIZE;
>> +        s->cplus_txbuffer_len = CP_TX_BUFFER_SIZE + VLAN_HDR_LEN;
>>           s->cplus_txbuffer = qemu_malloc(s->cplus_txbuffer_len);
>>           s->cplus_txbuffer_offset = 0;
>>
>>           DEBUG_PRINT(("RTL8139: +++ C+ mode transmission buffer
>> allocated space %d\n", s->cplus_txbuffer_len));
>>       }
>>
>> -    while (s->cplus_txbuffer&&  s->cplus_txbuffer_offset + txsize>=
>> s->cplus_txbuffer_len)
>> +    while (s->cplus_txbuffer&&  s->cplus_txbuffer_offset + txsize +
>> +        vlan_extra_size>= s->cplus_txbuffer_len)
>>       {
>>           s->cplus_txbuffer_len += CP_TX_BUFFER_SIZE;
>>           s->cplus_txbuffer = qemu_realloc(s->cplus_txbuffer,
>> s->cplus_txbuffer_len);
>> @@ -2025,6 +2037,20 @@ static int
>> rtl8139_cplus_transmit_one(RTL8139State *s)
>>       DEBUG_PRINT(("RTL8139: +++ C+ mode transmit reading %d bytes
>> from host memory at %016" PRIx64 " to offset %d\n",
>>                    txsize, (uint64_t)tx_addr, s->cplus_txbuffer_offset));
>>
>> +    if (vlan_extra_size&&  txsize>= 2 * ETHER_ADDR_LEN)
>> +    {
>> +        /* copy addresses */
>> +        cpu_physical_memory_read(tx_addr, s->cplus_txbuffer, 2 *
>> +            ETHER_ADDR_LEN);
>> +        tx_addr += 2 * ETHER_ADDR_LEN;
>> +        txsize -= 2 * ETHER_ADDR_LEN;
>> +        /* insert vlan tag */
>> +        *(uint16_t *)(s->cplus_txbuffer + 2 * ETHER_ADDR_LEN) =
>> +            cpu_to_be16(ETHERTYPE_VLAN);
>> +        *(uint16_t *)(s->cplus_txbuffer + 2 * ETHER_ADDR_LEN +
>> ETHER_TYPE_LEN)
>> +            = cpu_to_le16(txdw1&  CP_TX_VLAN_TAG_MASK);
>>    
> 
> This looks wrong.  You check for txsize >= 2 * ETHER_ADDR_LEN but then
> you assign at 2 * ETHER_ADDR_LEN.  This is a potential overflow, no?
> 

No, the check is to protect the read. Concerning the writes,
cplus_txbuffer is allocated with size of at least CP_TX_BUFFER_SIZE +
VLAN_HDR_LEN > 2 * ETHER_ADDR_LEN + VLAN_HDR_LEN (ie. 64k + 4 > 12 + 4),
please see previous hunk.

Thanks,
-Ben

> Regards,
> 
> Anthony Liguori
> 
>> +        s->cplus_txbuffer_offset += 2 * ETHER_ADDR_LEN + VLAN_HDR_LEN;
>> +    }
>>       cpu_physical_memory_read(tx_addr, s->cplus_txbuffer +
>> s->cplus_txbuffer_offset, txsize);
>>       s->cplus_txbuffer_offset += txsize;
>>
>> @@ -2053,9 +2079,6 @@ static int
>> rtl8139_cplus_transmit_one(RTL8139State *s)
>>       /* update ring data */
>>       val = cpu_to_le32(txdw0);
>>       cpu_physical_memory_write(cplus_tx_ring_desc,    (uint8_t
>> *)&val, 4);
>> -    /* TODO: implement VLAN tagging support, VLAN tag data is read to
>> txdw1 */
>> -//    val = cpu_to_le32(txdw1);
>> -//    cpu_physical_memory_write(cplus_tx_ring_desc+4,&val, 4);
>>
>>       /* Now decide if descriptor being processed is holding the last
>> segment of packet */
>>       if (txdw0&  CP_TX_LS)
>>    
>