Add netlinksafe

A wrapper to add retry on for netlink when it receives a ErrDumpInterrupted

Signed-off-by: Adrian Moisey <adrian@changeover.za.net>

pkg/netlinksafe/netlink.go

@@ -0,0 +1,321 @@
+// Package netlinksafe wraps vishvandanda/netlink functions that may return EINTR.
+//
+// A Handle instantiated using [NewHandle] or [NewHandleAt] can be used in place
+// of a netlink.Handle, it's a wrapper that replaces methods that need to be
+// wrapped. Functions that use the package handle need to be called as "netlinksafe.X"
+// instead of "netlink.X".
+//
+// The wrapped functions currently return EINTR when NLM_F_DUMP_INTR flagged
+// in a netlink response, meaning something changed during the dump so results
+// may be incomplete or inconsistent.
+//
+// At present, the possibly incomplete/inconsistent results are not returned
+// by netlink functions along with the EINTR. So, it's not possible to do
+// anything but retry. After maxAttempts the EINTR will be returned to the
+// caller.
+package netlinksafe
+
+import (
+	"log"
+
+	"github.com/pkg/errors"
+	"github.com/vishvananda/netlink"
+	"github.com/vishvananda/netlink/nl"
+	"github.com/vishvananda/netns"
+)
+
+// Arbitrary limit on max attempts at netlink calls if they are repeatedly interrupted.
+const maxAttempts = 5
+
+type Handle struct {
+	*netlink.Handle
+}
+
+func NewHandle(nlFamilies ...int) (Handle, error) {
+	nlh, err := netlink.NewHandle(nlFamilies...)
+	if err != nil {
+		return Handle{}, err
+	}
+	return Handle{nlh}, nil
+}
+
+func NewHandleAt(ns netns.NsHandle, nlFamilies ...int) (Handle, error) {
+	nlh, err := netlink.NewHandleAt(ns, nlFamilies...)
+	if err != nil {
+		return Handle{}, err
+	}
+	return Handle{nlh}, nil
+}
+
+func (h Handle) Close() {
+	if h.Handle != nil {
+		h.Handle.Close()
+	}
+}
+
+func retryOnIntr(f func() error) {
+	for attempt := 0; attempt < maxAttempts; attempt++ {
+		if err := f(); !errors.Is(err, netlink.ErrDumpInterrupted) {
+			return
+		}
+	}
+	log.Printf("netlink call interrupted after %d attempts", maxAttempts)
+}
+
+func discardErrDumpInterrupted(err error) error {
+	if errors.Is(err, netlink.ErrDumpInterrupted) {
+		// The netlink function has returned possibly-inconsistent data along with the
+		// error. Discard the error and return the data. This restores the behaviour of
+		// the netlink package prior to v1.2.1, in which NLM_F_DUMP_INTR was ignored in
+		// the netlink response.
+		log.Printf("discarding ErrDumpInterrupted: %+v", errors.WithStack(err))
+		return nil
+	}
+	return err
+}
+
+// AddrList calls netlink.AddrList, retrying if necessary.
+func AddrList(link netlink.Link, family int) ([]netlink.Addr, error) {
+	var addrs []netlink.Addr
+	var err error
+	retryOnIntr(func() error {
+		addrs, err = netlink.AddrList(link, family) //nolint:forbidigo
+		return err
+	})
+	return addrs, discardErrDumpInterrupted(err)
+}
+
+// LinkByName calls h.Handle.LinkByName, retrying if necessary. The netlink function
+// doesn't normally ask the kernel for a dump of links. But, on an old kernel, it
+// will do as a fallback and that dump may get inconsistent results.
+func (h Handle) LinkByName(name string) (netlink.Link, error) {
+	var link netlink.Link
+	var err error
+	retryOnIntr(func() error {
+		link, err = h.Handle.LinkByName(name) //nolint:forbidigo
+		return err
+	})
+	return link, discardErrDumpInterrupted(err)
+}
+
+// LinkByName calls netlink.LinkByName, retrying if necessary. The netlink
+// function doesn't normally ask the kernel for a dump of links. But, on an old
+// kernel, it will do as a fallback and that dump may get inconsistent results.
+func LinkByName(name string) (netlink.Link, error) {
+	var link netlink.Link
+	var err error
+	retryOnIntr(func() error {
+		link, err = netlink.LinkByName(name) //nolint:forbidigo
+		return err
+	})
+	return link, discardErrDumpInterrupted(err)
+}
+
+// LinkList calls h.Handle.LinkList, retrying if necessary.
+func (h Handle) LinkList() ([]netlink.Link, error) {
+	var links []netlink.Link
+	var err error
+	retryOnIntr(func() error {
+		links, err = h.Handle.LinkList() //nolint:forbidigo
+		return err
+	})
+	return links, discardErrDumpInterrupted(err)
+}
+
+// LinkList calls netlink.Handle.LinkList, retrying if necessary.
+func LinkList() ([]netlink.Link, error) {
+	var links []netlink.Link
+	var err error
+	retryOnIntr(func() error {
+		links, err = netlink.LinkList() //nolint:forbidigo
+		return err
+	})
+	return links, discardErrDumpInterrupted(err)
+}
+
+// RouteList calls h.Handle.RouteList, retrying if necessary.
+func (h Handle) RouteList(link netlink.Link, family int) ([]netlink.Route, error) {
+	var routes []netlink.Route
+	var err error
+	retryOnIntr(func() error {
+		routes, err = h.Handle.RouteList(link, family) //nolint:forbidigo
+		return err
+	})
+	return routes, err
+}
+
+// RouteList calls netlink.RouteList, retrying if necessary.
+func RouteList(link netlink.Link, family int) ([]netlink.Route, error) {
+	var route []netlink.Route
+	var err error
+	retryOnIntr(func() error {
+		route, err = netlink.RouteList(link, family) //nolint:forbidigo
+		return err
+	})
+	return route, discardErrDumpInterrupted(err)
+}
+
+// BridgeVlanList calls netlink.BridgeVlanList, retrying if necessary.
+func BridgeVlanList() (map[int32][]*nl.BridgeVlanInfo, error) {
+	var err error
+	var info map[int32][]*nl.BridgeVlanInfo
+	retryOnIntr(func() error {
+		info, err = netlink.BridgeVlanList() //nolint:forbidigo
+		return err
+	})
+	return info, discardErrDumpInterrupted(err)
+}
+
+// RouteListFiltered calls h.Handle.RouteListFiltered, retrying if necessary.
+func (h Handle) RouteListFiltered(family int, filter *netlink.Route, filterMask uint64) ([]netlink.Route, error) {
+	var routes []netlink.Route
+	var err error
+	retryOnIntr(func() error {
+		routes, err = h.Handle.RouteListFiltered(family, filter, filterMask) //nolint:forbidigo
+		return err
+	})
+	return routes, err
+}
+
+// RouteListFiltered calls netlink.RouteListFiltered, retrying if necessary.
+func RouteListFiltered(family int, filter *netlink.Route, filterMask uint64) ([]netlink.Route, error) {
+	var route []netlink.Route
+	var err error
+	retryOnIntr(func() error {
+		route, err = netlink.RouteListFiltered(family, filter, filterMask) //nolint:forbidigo
+		return err
+	})
+	return route, discardErrDumpInterrupted(err)
+}
+
+// QdiscList calls netlink.QdiscList, retrying if necessary.
+func QdiscList(link netlink.Link) ([]netlink.Qdisc, error) {
+	var qdisc []netlink.Qdisc
+	var err error
+	retryOnIntr(func() error {
+		qdisc, err = netlink.QdiscList(link) //nolint:forbidigo
+		return err
+	})
+	return qdisc, discardErrDumpInterrupted(err)
+}
+
+// QdiscList calls h.Handle.QdiscList, retrying if necessary.
+func (h *Handle) QdiscList(link netlink.Link) ([]netlink.Qdisc, error) {
+	var qdisc []netlink.Qdisc
+	var err error
+	retryOnIntr(func() error {
+		qdisc, err = h.Handle.QdiscList(link) //nolint:forbidigo
+		return err
+	})
+	return qdisc, err
+}
+
+// LinkGetProtinfo calls netlink.LinkGetProtinfo, retrying if necessary.
+func LinkGetProtinfo(link netlink.Link) (netlink.Protinfo, error) {
+	var protinfo netlink.Protinfo
+	var err error
+	retryOnIntr(func() error {
+		protinfo, err = netlink.LinkGetProtinfo(link) //nolint:forbidigo
+		return err
+	})
+	return protinfo, discardErrDumpInterrupted(err)
+}
+
+// LinkGetProtinfo calls h.Handle.LinkGetProtinfo, retrying if necessary.
+func (h *Handle) LinkGetProtinfo(link netlink.Link) (netlink.Protinfo, error) {
+	var protinfo netlink.Protinfo
+	var err error
+	retryOnIntr(func() error {
+		protinfo, err = h.Handle.LinkGetProtinfo(link) //nolint:forbidigo
+		return err
+	})
+	return protinfo, err
+}
+
+// RuleListFiltered calls netlink.RuleListFiltered, retrying if necessary.
+func RuleListFiltered(family int, filter *netlink.Rule, filterMask uint64) ([]netlink.Rule, error) {
+	var rules []netlink.Rule
+	var err error
+	retryOnIntr(func() error {
+		rules, err = netlink.RuleListFiltered(family, filter, filterMask) //nolint:forbidigo
+		return err
+	})
+	return rules, discardErrDumpInterrupted(err)
+}
+
+// RuleListFiltered calls h.Handle.RuleListFiltered, retrying if necessary.
+func (h *Handle) RuleListFiltered(family int, filter *netlink.Rule, filterMask uint64) ([]netlink.Rule, error) {
+	var rules []netlink.Rule
+	var err error
+	retryOnIntr(func() error {
+		rules, err = h.Handle.RuleListFiltered(family, filter, filterMask) //nolint:forbidigo
+		return err
+	})
+	return rules, err
+}
+
+// FilterList calls netlink.FilterList, retrying if necessary.
+func FilterList(link netlink.Link, parent uint32) ([]netlink.Filter, error) {
+	var filters []netlink.Filter
+	var err error
+	retryOnIntr(func() error {
+		filters, err = netlink.FilterList(link, parent) //nolint:forbidigo
+		return err
+	})
+	return filters, discardErrDumpInterrupted(err)
+}
+
+// FilterList calls h.Handle.FilterList, retrying if necessary.
+func (h *Handle) FilterList(link netlink.Link, parent uint32) ([]netlink.Filter, error) {
+	var filters []netlink.Filter
+	var err error
+	retryOnIntr(func() error {
+		filters, err = h.Handle.FilterList(link, parent) //nolint:forbidigo
+		return err
+	})
+	return filters, err
+}
+
+// RuleList calls netlink.RuleList, retrying if necessary.
+func RuleList(family int) ([]netlink.Rule, error) {
+	var rules []netlink.Rule
+	var err error
+	retryOnIntr(func() error {
+		rules, err = netlink.RuleList(family) //nolint:forbidigo
+		return err
+	})
+	return rules, discardErrDumpInterrupted(err)
+}
+
+// RuleList calls h.Handle.RuleList, retrying if necessary.
+func (h *Handle) RuleList(family int) ([]netlink.Rule, error) {
+	var rules []netlink.Rule
+	var err error
+	retryOnIntr(func() error {
+		rules, err = h.Handle.RuleList(family) //nolint:forbidigo
+		return err
+	})
+	return rules, err
+}
+
+// ConntrackDeleteFilters calls netlink.ConntrackDeleteFilters, retrying if necessary.
+func ConntrackDeleteFilters(table netlink.ConntrackTableType, family netlink.InetFamily, filters ...netlink.CustomConntrackFilter) (uint, error) {
+	var deleted uint
+	var err error
+	retryOnIntr(func() error {
+		deleted, err = netlink.ConntrackDeleteFilters(table, family, filters...) //nolint:forbidigo
+		return err
+	})
+	return deleted, discardErrDumpInterrupted(err)
+}
+
+// ConntrackDeleteFilters calls h.Handle.ConntrackDeleteFilters, retrying if necessary.
+func (h *Handle) ConntrackDeleteFilters(table netlink.ConntrackTableType, family netlink.InetFamily, filters ...netlink.CustomConntrackFilter) (uint, error) {
+	var deleted uint
+	var err error
+	retryOnIntr(func() error {
+		deleted, err = h.Handle.ConntrackDeleteFilters(table, family, filters...) //nolint:forbidigo
+		return err
+	})
+	return deleted, err
+}