diff options
Diffstat (limited to 'tap.h')
| -rw-r--r-- | tap.h | 25 |
1 files changed, 25 insertions, 0 deletions
@@ -6,6 +6,31 @@ #ifndef TAP_H #define TAP_H +/** L2_MAX_LEN_PASTA - Maximum frame length for pasta mode (with L2 header) + * + * The kernel tuntap device imposes a maximum frame size of 65535 including + * 'hard_header_len' (14 bytes for L2 Ethernet in the case of "tap" mode). + */ +#define L2_MAX_LEN_PASTA USHRT_MAX + +/** L2_MAX_LEN_PASST - Maximum frame length for passt mode (with L2 header) + * + * The only structural limit the QEMU socket protocol imposes on frames is + * (2^32-1) bytes, but that would be ludicrously long in practice. For now, + * limit it somewhat arbitrarily to 65535 bytes. FIXME: Work out an appropriate + * limit with more precision. + */ +#define L2_MAX_LEN_PASST USHRT_MAX + +/** L2_MAX_LEN_VU - Maximum frame length for vhost-user mode (with L2 header) + * + * vhost-user allows multiple buffers per frame, each of which can be quite + * large, so the inherent frame size limit is rather large. Much larger than is + * actually useful for IP. For now limit arbitrarily to 65535 bytes. FIXME: + * Work out an appropriate limit with more precision. + */ +#define L2_MAX_LEN_VU USHRT_MAX + struct udphdr; /** |