> Now that we can rely on do_not_pad being correct for all > NetClientInfo structs, we can pad short packets in the > qemu_send_packet() and qemu_sendv_packet() family of functions. > > If the callsite is already padding, then this will have no effect, > but callsites like the socket and dgram backends will now correctly > add padding. This fixes the bug where when two QEMU instances are > connected via one of those backends a short ARP packet transmitted by > one is not correctly padded by the other and gets dropped. > > Note that if we pad a packet, our return value on success will > be the size of the padded packet, not the original. This is OK > because this function (like the NetQueueDeliverFunc function type > documented in include/net/queue.h and which we will eventually > end up calling and returning the return value of) returns > >0 - success > 0 - queue packet for future redelivery > <0 - failure (discard packet) > and doesn't guarantee to return exactly the size of the packet > sent. None of the callers try to use the return value as an > exact size. > > Cc: [email protected] > Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/2362 > Signed-off-by: Peter Maydell <[email protected]> > Message-ID: <[email protected]> > --- > include/net/eth.h | 22 ++++++++++++++++++++++ > net/eth.c | 18 ++++++++++++++++++ > net/net.c | 22 ++++++++++++++++++++++ > 3 files changed, 62 insertions(+) > > diff --git a/include/net/eth.h b/include/net/eth.h > index 46dc9ed5acd9..042b2fc42db4 100644 > --- a/include/net/eth.h > +++ b/include/net/eth.h > @@ -437,4 +437,26 @@ eth_parse_ipv6_hdr(const struct iovec *pkt, int > pkt_frags, > bool eth_pad_short_frame(uint8_t *padded_pkt, size_t *padded_buflen, > const void *pkt, size_t pkt_size); > > +/** > + * eth_pad_short_frame_iov - pad a short frame, iovec version > + * > + * This is equivalent to eth_pad_short_frame(), except that it works > + * on a packet stored in a struct iovec. > + * > + * If the Ethernet frame size is shorter than 60 bytes, it will be padded to > + * 60 bytes at the address @padded_pkt (and the caller will need to handle > + * it as a not-in-an-iovec packet). > + * > + * @padded_pkt: buffer address to hold the padded frame > + * @padded_buflen: pointer holding length of @padded_pkt. If the frame is > + * padded, the length will be updated to the padded one. > + * @iov: iovec holding the original Ethernet frame > + * @iovcnt: number of elements in @iov > + * @pkt_size: size of the original Ethernet frame (i.e. iov_size(iov, > iovcnt)) > + * @return true if the frame is padded, otherwise false > + */ > +bool eth_pad_short_frame_iov(uint8_t *padded_pkt, size_t *padded_buflen, > + const struct iovec *iov, int iovcnt, > + size_t pkt_size); > + > #endif > diff --git a/net/eth.c b/net/eth.c > index 12ec316e240e..14006222d68d 100644 > --- a/net/eth.c > +++ b/net/eth.c > @@ -536,3 +536,21 @@ bool eth_pad_short_frame(uint8_t *padded_pkt, size_t > *padded_buflen, > > return true; > } > + > +bool eth_pad_short_frame_iov(uint8_t *padded_pkt, size_t *padded_buflen, > + const struct iovec *iov, int iovcnt, > + size_t pkt_size) > +{ > + assert(padded_buflen && *padded_buflen >= ETH_ZLEN); > + > + if (pkt_size >= ETH_ZLEN) { > + return false; > + } > + > + /* pad to minimum Ethernet frame length */ > + iov_to_buf(iov, iovcnt, 0, padded_pkt, pkt_size); > + memset(&padded_pkt[pkt_size], 0, ETH_ZLEN - pkt_size); > + *padded_buflen = ETH_ZLEN; > + > + return true;
assert(pkt_size == iov_size(iov, iovcnt)) or just drop pkt_size argument and comput it? Reviewed-by: Marc-André Lureau <[email protected]> -- Marc-André Lureau <[email protected]>
