On 2014/11/20 16:11, Jason Wang wrote: > On 11/20/2014 04:05 PM, Gonglei wrote: >> On 2014/11/20 15:50, Jason Wang wrote: >> >>>>> Maybe just initialize iov unconditionally at the beginning and check >>>>>>> dot1q_buf instead of iov for the rest of the functions. (Need deal with >>>>>>> size < ETHER_ADDR_LEN * 2) >>>>> More complicated, because we can't initialize iov when >>>>> "size < ETHER_ADDR_LEN * 2". >>>>> >>>>> Best regards, >>>>> -Gonglei >>>>> >>> Probably not: you can just do something like: >>> >>> if (dot1q_buf && size < ETHER_ADDR_LEN * 2) { >>> dot1q_buf = NULL; >>> } >>> >>> and check dot1q_buf afterwards. Or just drop the packet since its size >>> was less than mininum frame length that Ethernet allows. >> Sorry, I don't understand. But, >> what's your meaning "initialize iov unconditionally at the beginning"? > > Something like: > > @@ -1774,7 +1774,12 @@ static uint32_t > rtl8139_RxConfig_read(RTL8139State *s) > static void rtl8139_transfer_frame(RTL8139State *s, uint8_t *buf, int size, > int do_interrupt, const uint8_t *dot1q_buf) > { > - struct iovec *iov = NULL; > + struct iovec iov[3] = { > + { .iov_base = buf, .iov_len = ETHER_ADDR_LEN * 2 }, > + { .iov_base = (void *) dot1q_buf, .iov_len = VLAN_HLEN }, > + { .iov_base = buf + ETHER_ADDR_LEN * 2, > + .iov_len = size - ETHER_ADDR_LEN * 2 }, > + }; > > and assign dot1q_buf to NULL is size is not ok. >
If "size < ETHER_ADDR_LEN * 2", .iov_len = size - ETHER_ADDR_LEN * 2 will be negative value; and if dot1q_buf is NULL, .iov_base = (void *) dot1q_buf will be NULL too. Any side-effect? > Just a suggestion, your call. Thanks, Jason :) Best regards, -Gonglei