Fix minor bugs in a couple of interface IOCTLs.

gVisor incorrectly returns the wrong ARP type for SIOGIFHWADDR. This breaks
tcpdump as it tries to interpret the packets incorrectly.

Similarly, SIOCETHTOOL is used by tcpdump to query interface properties which
fails with an EINVAL since we don't implement it. For now change it to return
EOPNOTSUPP to indicate that we don't support the query rather than return
EINVAL.

NOTE: ARPHRD types for link endpoints are distinct from NIC capabilities
and NIC flags. In Linux all 3 exist eg. ARPHRD types are stored in dev->type
field while NIC capabilities are more like the device features which can be
queried using SIOCETHTOOL but not modified and NIC Flags are fields that can
be modified from user space. eg. NIC status (UP/DOWN/MULTICAST/BROADCAST) etc.

Updates #2746

PiperOrigin-RevId: 321436525

2 files changed, 7 insertions, 0 deletions

diff --git a/pkg/tcpip/link/qdisc/fifo/BUILD b/pkg/tcpip/link/qdisc/fifo/BUILD
index 054c213bc..1d0079bd6 100644
--- a/pkg/tcpip/link/qdisc/fifo/BUILD
+++ b/pkg/tcpip/link/qdisc/fifo/BUILD
@@ -14,6 +14,7 @@ go_library(
         "//pkg/sync",
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
+        "//pkg/tcpip/header",
         "//pkg/tcpip/stack",
     ],
 )
diff --git a/pkg/tcpip/link/qdisc/fifo/endpoint.go b/pkg/tcpip/link/qdisc/fifo/endpoint.go
index b5dfb7850..c84fe1bb9 100644
--- a/pkg/tcpip/link/qdisc/fifo/endpoint.go
+++ b/pkg/tcpip/link/qdisc/fifo/endpoint.go
@@ -22,6 +22,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
 
@@ -207,3 +208,8 @@ func (e *endpoint) Wait() {
 
 	e.wg.Wait()
 }
+
+// ARPHardwareType implements stack.LinkEndpoint.ARPHardwareType
+func (e *endpoint) ARPHardwareType() header.ARPHardwareType {
+	return e.lower.ARPHardwareType()
+}