Process Hop-by-Hop header when forwarding IPv6 packets

Currently, we process IPv6 extension headers when receiving packets
but not when forwarding them. This is fine for the most part, with
with one exception: RFC 8200 requires that we process the
Hop-by-Hop headers even while forwarding packets.

This CL adds that support by invoking the Hop-by-hop logic performed
when receiving packets during forwarding as well.

PiperOrigin-RevId: 373145478

2 files changed, 25 insertions, 15 deletions

diff --git a/pkg/tcpip/network/internal/ip/errors.go b/pkg/tcpip/network/internal/ip/errors.go
index 50fabfd79..d3577b377 100644
--- a/pkg/tcpip/network/internal/ip/errors.go
+++ b/pkg/tcpip/network/internal/ip/errors.go
@@ -34,13 +34,13 @@ func (*ErrTTLExceeded) isForwardingError() {}
 
 func (*ErrTTLExceeded) String() string { return "ttl exceeded" }
 
-// ErrIPOptProblem indicates the received packet had a problem with an IP
-// option.
-type ErrIPOptProblem struct{}
+// ErrParameterProblem indicates the received packet had a problem with an IP
+// parameter.
+type ErrParameterProblem struct{}
 
-func (*ErrIPOptProblem) isForwardingError() {}
+func (*ErrParameterProblem) isForwardingError() {}
 
-func (*ErrIPOptProblem) String() string { return "ip option problem" }
+func (*ErrParameterProblem) String() string { return "parameter problem" }
 
 // ErrLinkLocalSourceAddress indicates the received packet had a link-local
 // source address.
diff --git a/pkg/tcpip/network/internal/ip/stats.go b/pkg/tcpip/network/internal/ip/stats.go
index 392f0b0c7..68b8b550e 100644
--- a/pkg/tcpip/network/internal/ip/stats.go
+++ b/pkg/tcpip/network/internal/ip/stats.go
@@ -16,7 +16,7 @@ package ip
 
 import "gvisor.dev/gvisor/pkg/tcpip"
 
-// LINT.IfChange(MultiCounterIPStats)
+// LINT.IfChange(MultiCounterIPForwardingStats)
 
 // MultiCounterIPForwardingStats holds IP forwarding statistics. Each counter
 // may have several versions.
@@ -38,11 +38,30 @@ type MultiCounterIPForwardingStats struct {
 	// because they contained a link-local destination address.
 	LinkLocalDestination tcpip.MultiCounterStat
 
+	// ExtensionHeaderProblem is the number of IP packets which were dropped
+	// because of a problem encountered when processing an IPv6 extension
+	// header.
+	ExtensionHeaderProblem tcpip.MultiCounterStat
+
 	// Errors is the number of IP packets received which could not be
 	// successfully forwarded.
 	Errors tcpip.MultiCounterStat
 }
 
+// Init sets internal counters to track a and b counters.
+func (m *MultiCounterIPForwardingStats) Init(a, b *tcpip.IPForwardingStats) {
+	m.Unrouteable.Init(a.Unrouteable, b.Unrouteable)
+	m.Errors.Init(a.Errors, b.Errors)
+	m.LinkLocalSource.Init(a.LinkLocalSource, b.LinkLocalSource)
+	m.LinkLocalDestination.Init(a.LinkLocalDestination, b.LinkLocalDestination)
+	m.ExtensionHeaderProblem.Init(a.ExtensionHeaderProblem, b.ExtensionHeaderProblem)
+	m.ExhaustedTTL.Init(a.ExhaustedTTL, b.ExhaustedTTL)
+}
+
+// LINT.ThenChange(:MultiCounterIPForwardingStats, ../../../tcpip.go:IPForwardingStats)
+
+// LINT.IfChange(MultiCounterIPStats)
+
 // MultiCounterIPStats holds IP statistics, each counter may have several
 // versions.
 type MultiCounterIPStats struct {
@@ -120,15 +139,6 @@ type MultiCounterIPStats struct {
 }
 
 // Init sets internal counters to track a and b counters.
-func (m *MultiCounterIPForwardingStats) Init(a, b *tcpip.IPForwardingStats) {
-	m.Unrouteable.Init(a.Unrouteable, b.Unrouteable)
-	m.Errors.Init(a.Errors, b.Errors)
-	m.LinkLocalSource.Init(a.LinkLocalSource, b.LinkLocalSource)
-	m.LinkLocalDestination.Init(a.LinkLocalDestination, b.LinkLocalDestination)
-	m.ExhaustedTTL.Init(a.ExhaustedTTL, b.ExhaustedTTL)
-}
-
-// Init sets internal counters to track a and b counters.
 func (m *MultiCounterIPStats) Init(a, b *tcpip.IPStats) {
 	m.PacketsReceived.Init(a.PacketsReceived, b.PacketsReceived)
 	m.DisabledPacketsReceived.Init(a.DisabledPacketsReceived, b.DisabledPacketsReceived)