Re: [PATCH 2/7] Separately locate external interfaces for IPv4 and IPv6

[Stefano Brivio <sbrivio@redhat.com>]

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On Fri, 22 Jul 2022 15:31:13 +1000
David Gibson <david(a)gibson.dropbear.id.au> wrote:

> Now that the back end allows passt/pasta to use different external
> interfaces for IPv4 and IPv6, use that to do the right thing in the case
> that the host has IPv4 and IPv6 connectivity via different interfaces.
> If the user hasn't explicitly chosen an interface, separately search for
> a suitable external interface for each protocol.
> 
> As a bonus, this substantially simplifies the external interface probe.  It
> also eliminates a subtle confusing case where in some circumstances we
> would pick the first interface in interface index order, and sometimes in
> order of routes returned from netlink.  On some network configurations that
> could cause tests to fail, because the logic in the tests was subtly
> different (it always used route order).
> 
> Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
> ---
>  conf.c                | 19 +++++++++--
>  netlink.c             | 79 ++++---------------------------------------
>  netlink.h             |  2 +-
>  test/dhcp/passt       |  3 +-
>  test/dhcp/pasta       |  3 +-
>  test/ndp/passt        |  4 +--
>  test/two_guests/basic |  3 +-
>  7 files changed, 33 insertions(+), 80 deletions(-)
> 
> [...]
>
> diff --git a/test/dhcp/passt b/test/dhcp/passt
> index f45227a..11e0eb3 100644
> --- a/test/dhcp/passt
> +++ b/test/dhcp/passt
> @@ -17,6 +17,7 @@ htools	ip jq sed tr head
>  test	Interface name
>  gout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
>  hout	HOST_IFNAME ip -j -4 route show|jq -rM '[.[] | select(.dst == "default").dev] | .[0]'
> +hout	HOST_IFNAME6 ip -j -6 route show|jq -rM '[.[] | select(.dst == "default").dev] | .[0]'
>  check	[ -n "__IFNAME__" ]
>  
>  test	DHCP: address
> @@ -49,7 +50,7 @@ check	[ "__SEARCH__" = "__HOST_SEARCH__" ]
>  test	DHCPv6: address
>  guest	/sbin/dhclient -6 __IFNAME__
>  gout	ADDR6 ip -j -6 addr show|jq -rM '.[] | select(.ifname == "__IFNAME__").addr_info[] | select(.prefixlen == 128).local'
> -hout	HOST_ADDR6 ip -j -6 addr show|jq -rM '.[] | select(.ifname == "__HOST_IFNAME__").addr_info[] | select(.scope == "global").local'
> +hout	HOST_ADDR6 ip -j -6 addr show|jq -rM '.[] | select(.ifname == "__HOST_IFNAME6__").addr_info[] | select(.scope == "global").local'
>  check	[ "__ADDR6__" = "__HOST_ADDR6__" ]
>  
>  test	DHCPv6: route

This,

> [...]
> 
> diff --git a/test/two_guests/basic b/test/two_guests/basic
> index f7c016d..e226178 100644
> --- a/test/two_guests/basic
> +++ b/test/two_guests/basic
> @@ -19,6 +19,7 @@ test	Interface names
>  g1out	IFNAME1 ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
>  g2out	IFNAME2 ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
>  hout	HOST_IFNAME ip -j -4 route show|jq -rM '[.[] | select(.dst == "default").dev] | .[0]'
> +hout	HOST_IFNAME6 ip -j -6 route show|jq -rM '[.[] | select(.dst == "default").dev] | .[0]'
>  check	[ -n "__IFNAME1__" ]
>  check	[ -n "__IFNAME2__" ]
>  
> @@ -40,7 +41,7 @@ guest1	/sbin/dhclient -6 __IFNAME1__
>  guest2	/sbin/dhclient -6 __IFNAME2__
>  g1out	ADDR1_6 ip -j -6 addr show|jq -rM '.[] | select(.ifname == "__IFNAME1__").addr_info[] | select(.prefixlen == 128).local'
>  g2out	ADDR2_6 ip -j -6 addr show|jq -rM '.[] | select(.ifname == "__IFNAME2__").addr_info[] | select(.prefixlen == 128).local'
> -hout	HOST_ADDR6 ip -j -6 addr show|jq -rM '.[] | select(.ifname == "__HOST_IFNAME__").addr_info[] | select(.scope == "global").local'
> +hout	HOST_ADDR6 ip -j -6 addr show|jq -rM '.[] | select(.ifname == "__HOST_IFNAME6__").addr_info[] | select(.scope == "global").local'
>  check	[ "__ADDR1_6__" = "__HOST_ADDR6__" ]
>  check	[ "__ADDR2_6__" = "__HOST_ADDR6__" ]
>  

and this are based on patch 17/18 from your previous series ("tests:
Correct determination of host interface name in tests"). I went ahead
and applied that patch (which I skipped previously) before this one,
anyway it makes sense now.

-- 
Stefano