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| 1 | +// Package nlwrap wraps vishvandanda/netlink functions that may return EINTR. |
| 2 | +// |
| 3 | +// A Handle instantiated using [NewHandle] or [NewHandleAt] can be used in place |
| 4 | +// of a netlink.Handle, it's a wrapper that replaces methods that need to be |
| 5 | +// wrapped. Functions that use the package handle need to be called as "nlwrap.X" |
| 6 | +// instead of "netlink.X". |
| 7 | +// |
| 8 | +// The wrapped functions currently return EINTR when NLM_F_DUMP_INTR flagged |
| 9 | +// in a netlink response, meaning something changed during the dump so results |
| 10 | +// may be incomplete or inconsistent. |
| 11 | +// |
| 12 | +// At present, the possibly incomplete/inconsistent results are not returned |
| 13 | +// by netlink functions along with the EINTR. So, it's not possible to do |
| 14 | +// anything but retry. After maxAttempts the EINTR will be returned to the |
| 15 | +// caller. |
| 16 | +package nlwrap |
| 17 | + |
| 18 | +import ( |
| 19 | + "context" |
| 20 | + "errors" |
| 21 | + |
| 22 | + "github.com/containerd/log" |
| 23 | + "github.com/vishvananda/netlink" |
| 24 | + "github.com/vishvananda/netns" |
| 25 | + "golang.org/x/sys/unix" |
| 26 | +) |
| 27 | + |
| 28 | +// Arbitrary limit on max attempts at netlink calls if they are repeatedly interrupted. |
| 29 | +const maxAttempts = 5 |
| 30 | + |
| 31 | +type Handle struct { |
| 32 | + *netlink.Handle |
| 33 | +} |
| 34 | + |
| 35 | +func NewHandle(nlFamilies ...int) (Handle, error) { |
| 36 | + nlh, err := netlink.NewHandle(nlFamilies...) |
| 37 | + if err != nil { |
| 38 | + return Handle{}, err |
| 39 | + } |
| 40 | + return Handle{nlh}, nil |
| 41 | +} |
| 42 | + |
| 43 | +func NewHandleAt(ns netns.NsHandle, nlFamilies ...int) (Handle, error) { |
| 44 | + nlh, err := netlink.NewHandleAt(ns, nlFamilies...) |
| 45 | + if err != nil { |
| 46 | + return Handle{}, err |
| 47 | + } |
| 48 | + return Handle{nlh}, nil |
| 49 | +} |
| 50 | + |
| 51 | +func (h Handle) Close() { |
| 52 | + if h.Handle != nil { |
| 53 | + h.Handle.Close() |
| 54 | + } |
| 55 | +} |
| 56 | + |
| 57 | +func retryOnIntr(f func() error) { |
| 58 | + for attempt := 0; attempt < maxAttempts; attempt += 1 { |
| 59 | + if err := f(); !errors.Is(err, unix.EINTR) { |
| 60 | + return |
| 61 | + } |
| 62 | + } |
| 63 | + log.G(context.TODO()).Infof("netlink call interrupted after %d attempts", maxAttempts) |
| 64 | +} |
| 65 | + |
| 66 | +// AddrList calls nlh.LinkList, retrying if necessary. |
| 67 | +func (nlh Handle) AddrList(link netlink.Link, family int) (addrs []netlink.Addr, err error) { |
| 68 | + retryOnIntr(func() error { |
| 69 | + addrs, err = nlh.Handle.AddrList(link, family) |
| 70 | + return err |
| 71 | + }) |
| 72 | + return addrs, err |
| 73 | +} |
| 74 | + |
| 75 | +// AddrList calls netlink.LinkList, retrying if necessary. |
| 76 | +func AddrList(link netlink.Link, family int) (addrs []netlink.Addr, err error) { |
| 77 | + retryOnIntr(func() error { |
| 78 | + addrs, err = netlink.AddrList(link, family) |
| 79 | + return err |
| 80 | + }) |
| 81 | + return addrs, err |
| 82 | +} |
| 83 | + |
| 84 | +// ConntrackDeleteFilters calls nlh.ConntrackDeleteFilters, retrying if necessary. |
| 85 | +func (nlh Handle) ConntrackDeleteFilters( |
| 86 | + table netlink.ConntrackTableType, |
| 87 | + family netlink.InetFamily, |
| 88 | + filters ...netlink.CustomConntrackFilter, |
| 89 | +) (matched uint, err error) { |
| 90 | + retryOnIntr(func() error { |
| 91 | + matched, err = nlh.Handle.ConntrackDeleteFilters(table, family, filters...) |
| 92 | + return err |
| 93 | + }) |
| 94 | + return matched, err |
| 95 | +} |
| 96 | + |
| 97 | +// ConntrackTableList calls netlink.ConntrackTableList, retrying if necessary. |
| 98 | +func ConntrackTableList( |
| 99 | + table netlink.ConntrackTableType, |
| 100 | + family netlink.InetFamily, |
| 101 | +) (flows []*netlink.ConntrackFlow, err error) { |
| 102 | + retryOnIntr(func() error { |
| 103 | + flows, err = netlink.ConntrackTableList(table, family) |
| 104 | + return err |
| 105 | + }) |
| 106 | + return flows, err |
| 107 | +} |
| 108 | + |
| 109 | +// LinkByName calls nlh.LinkByName, retrying if necessary. The netlink function |
| 110 | +// doesn't normally ask the kernel for a dump of links. But, on an old kernel, it |
| 111 | +// will do as a fallback and that dump may get inconsistent results. |
| 112 | +func (nlh Handle) LinkByName(name string) (link netlink.Link, err error) { |
| 113 | + retryOnIntr(func() error { |
| 114 | + link, err = nlh.Handle.LinkByName(name) |
| 115 | + return err |
| 116 | + }) |
| 117 | + return link, err |
| 118 | +} |
| 119 | + |
| 120 | +// LinkByName calls netlink.LinkByName, retrying if necessary. The netlink |
| 121 | +// function doesn't normally ask the kernel for a dump of links. But, on an old |
| 122 | +// kernel, it will do as a fallback and that dump may get inconsistent results. |
| 123 | +func LinkByName(name string) (link netlink.Link, err error) { |
| 124 | + retryOnIntr(func() error { |
| 125 | + link, err = netlink.LinkByName(name) |
| 126 | + return err |
| 127 | + }) |
| 128 | + return link, err |
| 129 | +} |
| 130 | + |
| 131 | +// LinkList calls nlh.LinkList, retrying if necessary. |
| 132 | +func (nlh Handle) LinkList() (links []netlink.Link, err error) { |
| 133 | + retryOnIntr(func() error { |
| 134 | + links, err = nlh.Handle.LinkList() |
| 135 | + return err |
| 136 | + }) |
| 137 | + return links, err |
| 138 | +} |
| 139 | + |
| 140 | +// LinkList calls netlink.LinkList, retrying if necessary. |
| 141 | +func LinkList() (links []netlink.Link, err error) { |
| 142 | + retryOnIntr(func() error { |
| 143 | + links, err = netlink.LinkList() |
| 144 | + return err |
| 145 | + }) |
| 146 | + return links, err |
| 147 | +} |
| 148 | + |
| 149 | +// RouteList calls nlh.RouteList, retrying if necessary. |
| 150 | +func (nlh Handle) RouteList(link netlink.Link, family int) (routes []netlink.Route, err error) { |
| 151 | + retryOnIntr(func() error { |
| 152 | + routes, err = nlh.Handle.RouteList(link, family) |
| 153 | + return err |
| 154 | + }) |
| 155 | + return routes, err |
| 156 | +} |
| 157 | + |
| 158 | +func (nlh Handle) XfrmPolicyList(family int) (policies []netlink.XfrmPolicy, err error) { |
| 159 | + retryOnIntr(func() error { |
| 160 | + policies, err = nlh.Handle.XfrmPolicyList(family) |
| 161 | + return err |
| 162 | + }) |
| 163 | + return policies, err |
| 164 | +} |
| 165 | + |
| 166 | +func (nlh Handle) XfrmStateList(family int) (states []netlink.XfrmState, err error) { |
| 167 | + retryOnIntr(func() error { |
| 168 | + states, err = nlh.Handle.XfrmStateList(family) |
| 169 | + return err |
| 170 | + }) |
| 171 | + return states, err |
| 172 | +} |
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