Maksim Yevmenkin wrote:
Hello,
A quick question about if_tap, the tapwrite function ( which copies an ethernet frame into an mbuf using uiotombuf ) is broken on alpha and sparc64. The 14 byte ethernet header causes the rest of the frame to be misaligned on 4 byte boundaries. This causes crashes in various other parts of the kernel. The solution would be to shift the mbuf by two bytes, but I am not quite sure where this should happen.
i think we have few options here:
1) revert back original tapwrite function that was changed in v. 1.48 and set offset to 2 bytes in top mbuf
2) change current version of tapwrite so it would m_prepend and m_pullup mbuf after m_uiotombuf
3) change m_uiotombuf to accept one more parameter - mbuf offset at which data should be copied. there are not that many users of m_uiotombuf
/sys/kern/uipc_syscalls.c /sys/net/if_tap.c /sys/net/if_tun.c /sys/netgraph/ng_device.c
I think we should defien a MAC header that looks like: char dummy[2] char dest[6] char src[6] char type_len[2] and make ether net cards start writing 2 bytes into the buffer :-)
If_tun which is almost the same code has no such problem because it lacks the 14 byte ethernet header. Openbsd has a combined tun/tap driver, with some alignment hacks to fix this.
yes, that is true.
Should I create a pr for this problem, or is there a simple quick fix possible ?
you probably should file pr. (1) and (2) above are quick fixes. (3) is more complicated and, maybe, not desirable.
max _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "[EMAIL PROTECTED]"
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