From e8f30571a375777fc83c14602f9ed32ac26eedb4 Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Wed, 6 Sep 2017 23:56:22 +0100 Subject: [PATCH] [efi] Match behaviour of SnpDxe for truncated received packets The UEFI specification does not state whether or not a return value of EFI_BUFFER_TOO_SMALL from the SNP Receive() method should follow the usual EFI API behaviour of allowing the caller to retry the request with an increased buffer size. Examination of the SnpDxe driver in EDK2 suggests that Receive() will just return the truncated packet (complete with any requested link-layer header fields), so match this behaviour. Signed-off-by: Michael Brown --- src/interface/efi/efi_snp.c | 22 +++++++++------------- 1 file changed, 9 insertions(+), 13 deletions(-) diff --git a/src/interface/efi/efi_snp.c b/src/interface/efi/efi_snp.c index 5c3592e5..263a25ac 100644 --- a/src/interface/efi/efi_snp.c +++ b/src/interface/efi/efi_snp.c @@ -710,7 +710,7 @@ efi_snp_receive ( EFI_SIMPLE_NETWORK_PROTOCOL *snp, const void *iob_ll_src; uint16_t iob_net_proto; unsigned int iob_flags; - size_t max_len; + size_t copy_len; int rc; DBGC2 ( snpdev, "SNPDEV %p RECEIVE %p(+%lx)", snpdev, data, @@ -732,19 +732,15 @@ efi_snp_receive ( EFI_SIMPLE_NETWORK_PROTOCOL *snp, } DBGC2 ( snpdev, "+%zx\n", iob_len ( iobuf ) ); - /* Check buffer length */ - max_len = *len; - *len = iob_len ( iobuf ); - if ( *len > max_len ) { - rc = -ERANGE; - goto out_too_long; - } - /* Dequeue packet */ list_del ( &iobuf->list ); - /* Return packet to caller */ - memcpy ( data, iobuf->data, iob_len ( iobuf ) ); + /* Return packet to caller, truncating to buffer length */ + copy_len = iob_len ( iobuf ); + if ( copy_len > *len ) + copy_len = *len; + memcpy ( data, iobuf->data, copy_len ); + *len = iob_len ( iobuf ); /* Attempt to decode link-layer header */ if ( ( rc = ll_protocol->pull ( snpdev->netdev, iobuf, &iob_ll_dest, @@ -765,11 +761,11 @@ efi_snp_receive ( EFI_SIMPLE_NETWORK_PROTOCOL *snp, if ( net_proto ) *net_proto = ntohs ( iob_net_proto ); - rc = 0; + /* Check buffer length */ + rc = ( ( copy_len == *len ) ? 0 : -ERANGE ); out_bad_ll_header: free_iob ( iobuf ); - out_too_long: out_no_packet: return EFIRC ( rc ); }