svn commit: r363244 - head/sys/net

[Kyle Evans]

Author: kevans
Date: Thu Jul 16 13:37:32 2020
New Revision: 363244
URL: https://svnweb.freebsd.org/changeset/base/363244

Log:
  ether_ifattach: set mtu before calling if_attach()
  
  if_attach() -> if_attach_internal() will call if_attachdomain1(ifp) any time
  an ethernet interface is setup *after*
  SI_SUB_PROTO_IFATTACHDOMAIN/SI_ORDER_FIRST.  This eventually leads to
  nd6_ifattach() -> nd6_setmtu0() stashing off ifp->if_mtu in ndi->maxmtu
  *before* ifp->if_mtu has been properly set in some scenarios, e.g., USB
  ethernet adapter plugged in later on.
  
  For interfaces that are created in early boot, we don't have this issue as
  domains aren't constructed enough for them to attach and thus it gets
  deferred to domainifattach at SI_SUB_PROTO_IFATTACHDOMAIN/SI_ORDER_SECOND
  *after* the mtu has been set earlier in ether_ifattach().
  
  PR:		248005
  Submitted by:	Mathew <mjanelle blackberry com>
  MFC after:	1 week

Modified:
  head/sys/net/if_ethersubr.c

Modified: head/sys/net/if_ethersubr.c
==============================================================================
--- head/sys/net/if_ethersubr.c	Thu Jul 16 13:37:11 2020	(r363243)
+++ head/sys/net/if_ethersubr.c	Thu Jul 16 13:37:32 2020	(r363244)
@@ -969,8 +969,8 @@ ether_ifattach(struct ifnet *ifp, const u_int8_t *lla)
 
 	ifp->if_addrlen = ETHER_ADDR_LEN;
 	ifp->if_hdrlen = ETHER_HDR_LEN;
-	if_attach(ifp);
 	ifp->if_mtu = ETHERMTU;
+	if_attach(ifp);
 	ifp->if_output = ether_output;
 	ifp->if_input = ether_input;
 	ifp->if_resolvemulti = ether_resolvemulti;