From a085e562d0592bccc99e9e0380706a8025f70d53 Mon Sep 17 00:00:00 2001
From: Ian Gudger <igudger@google.com>
Date: Wed, 10 Jun 2020 23:48:03 -0700
Subject: Add support for SO_REUSEADDR to UDP sockets/endpoints.
On UDP sockets, SO_REUSEADDR allows multiple sockets to bind to the same
address, but only delivers packets to the most recently bound socket. This
differs from the behavior of SO_REUSEADDR on TCP sockets. SO_REUSEADDR for TCP
sockets will likely need an almost completely independent implementation.
SO_REUSEADDR has some odd interactions with the similar SO_REUSEPORT. These
interactions are tested fairly extensively and all but one particularly odd
one (that honestly seems like a bug) behave the same on gVisor and Linux.
PiperOrigin-RevId: 315844832
---
pkg/tcpip/ports/ports.go | 116 ++++++++++++++++++++++++++++++++---------------
1 file changed, 79 insertions(+), 37 deletions(-)
(limited to 'pkg/tcpip/ports')
diff --git a/pkg/tcpip/ports/ports.go b/pkg/tcpip/ports/ports.go
index b937cb84b..edc29ad27 100644
--- a/pkg/tcpip/ports/ports.go
+++ b/pkg/tcpip/ports/ports.go
@@ -54,17 +54,27 @@ type Flags struct {
LoadBalanced bool
}
-func (f Flags) bits() reuseFlag {
- var rf reuseFlag
+// Bits converts the Flags to their bitset form.
+func (f Flags) Bits() BitFlags {
+ var rf BitFlags
if f.MostRecent {
- rf |= mostRecentFlag
+ rf |= MostRecentFlag
}
if f.LoadBalanced {
- rf |= loadBalancedFlag
+ rf |= LoadBalancedFlag
}
return rf
}
+// Effective returns the effective behavior of a flag config.
+func (f Flags) Effective() Flags {
+ e := f
+ if e.LoadBalanced && e.MostRecent {
+ e.MostRecent = false
+ }
+ return e
+}
+
// PortManager manages allocating, reserving and releasing ports.
type PortManager struct {
mu sync.RWMutex
@@ -78,56 +88,88 @@ type PortManager struct {
hint uint32
}
-type reuseFlag int
+// BitFlags is a bitset representation of Flags.
+type BitFlags uint32
const (
- mostRecentFlag reuseFlag = 1 << iota
- loadBalancedFlag
+ // MostRecentFlag represents Flags.MostRecent.
+ MostRecentFlag BitFlags = 1 << iota
+
+ // LoadBalancedFlag represents Flags.LoadBalanced.
+ LoadBalancedFlag
+
+ // nextFlag is the value that the next added flag will have.
+ //
+ // It is used to calculate FlagMask below. It is also the number of
+ // valid flag states.
nextFlag
- flagMask = nextFlag - 1
+ // FlagMask is a bit mask for BitFlags.
+ FlagMask = nextFlag - 1
)
-type portNode struct {
- // refs stores the count for each possible flag combination.
+// ToFlags converts the bitset into a Flags struct.
+func (f BitFlags) ToFlags() Flags {
+ return Flags{
+ MostRecent: f&MostRecentFlag != 0,
+ LoadBalanced: f&LoadBalancedFlag != 0,
+ }
+}
+
+// FlagCounter counts how many references each flag combination has.
+type FlagCounter struct {
+ // refs stores the count for each possible flag combination, (0 though
+ // FlagMask).
refs [nextFlag]int
}
-func (p portNode) totalRefs() int {
+// AddRef increases the reference count for a specific flag combination.
+func (c *FlagCounter) AddRef(flags BitFlags) {
+ c.refs[flags]++
+}
+
+// DropRef decreases the reference count for a specific flag combination.
+func (c *FlagCounter) DropRef(flags BitFlags) {
+ c.refs[flags]--
+}
+
+// TotalRefs calculates the total number of references for all flag
+// combinations.
+func (c FlagCounter) TotalRefs() int {
var total int
- for _, r := range p.refs {
+ for _, r := range c.refs {
total += r
}
return total
}
-// flagRefs returns the number of references with all specified flags.
-func (p portNode) flagRefs(flags reuseFlag) int {
+// FlagRefs returns the number of references with all specified flags.
+func (c FlagCounter) FlagRefs(flags BitFlags) int {
var total int
- for i, r := range p.refs {
- if reuseFlag(i)&flags == flags {
+ for i, r := range c.refs {
+ if BitFlags(i)&flags == flags {
total += r
}
}
return total
}
-// allRefsHave returns if all references have all specified flags.
-func (p portNode) allRefsHave(flags reuseFlag) bool {
- for i, r := range p.refs {
- if reuseFlag(i)&flags == flags && r > 0 {
+// AllRefsHave returns if all references have all specified flags.
+func (c FlagCounter) AllRefsHave(flags BitFlags) bool {
+ for i, r := range c.refs {
+ if BitFlags(i)&flags != flags && r > 0 {
return false
}
}
return true
}
-// intersectionRefs returns the set of flags shared by all references.
-func (p portNode) intersectionRefs() reuseFlag {
- intersection := flagMask
- for i, r := range p.refs {
+// IntersectionRefs returns the set of flags shared by all references.
+func (c FlagCounter) IntersectionRefs() BitFlags {
+ intersection := FlagMask
+ for i, r := range c.refs {
if r > 0 {
- intersection &= reuseFlag(i)
+ intersection &= BitFlags(i)
}
}
return intersection
@@ -135,26 +177,26 @@ func (p portNode) intersectionRefs() reuseFlag {
// deviceNode is never empty. When it has no elements, it is removed from the
// map that references it.
-type deviceNode map[tcpip.NICID]portNode
+type deviceNode map[tcpip.NICID]FlagCounter
// isAvailable checks whether binding is possible by device. If not binding to a
-// device, check against all portNodes. If binding to a specific device, check
+// device, check against all FlagCounters. If binding to a specific device, check
// against the unspecified device and the provided device.
//
// If either of the port reuse flags is enabled on any of the nodes, all nodes
// sharing a port must share at least one reuse flag. This matches Linux's
// behavior.
func (d deviceNode) isAvailable(flags Flags, bindToDevice tcpip.NICID) bool {
- flagBits := flags.bits()
+ flagBits := flags.Bits()
if bindToDevice == 0 {
// Trying to binding all devices.
if flagBits == 0 {
// Can't bind because the (addr,port) is already bound.
return false
}
- intersection := flagMask
+ intersection := FlagMask
for _, p := range d {
- i := p.intersectionRefs()
+ i := p.IntersectionRefs()
intersection &= i
if intersection&flagBits == 0 {
// Can't bind because the (addr,port) was
@@ -165,17 +207,17 @@ func (d deviceNode) isAvailable(flags Flags, bindToDevice tcpip.NICID) bool {
return true
}
- intersection := flagMask
+ intersection := FlagMask
if p, ok := d[0]; ok {
- intersection = p.intersectionRefs()
+ intersection = p.IntersectionRefs()
if intersection&flagBits == 0 {
return false
}
}
if p, ok := d[bindToDevice]; ok {
- i := p.intersectionRefs()
+ i := p.IntersectionRefs()
intersection &= i
if intersection&flagBits == 0 {
return false
@@ -324,7 +366,7 @@ func (s *PortManager) reserveSpecificPort(networks []tcpip.NetworkProtocolNumber
if !s.isPortAvailableLocked(networks, transport, addr, port, flags, bindToDevice) {
return false
}
- flagBits := flags.bits()
+ flagBits := flags.Bits()
// Reserve port on all network protocols.
for _, network := range networks {
@@ -340,7 +382,7 @@ func (s *PortManager) reserveSpecificPort(networks []tcpip.NetworkProtocolNumber
m[addr] = d
}
n := d[bindToDevice]
- n.refs[flagBits]++
+ n.AddRef(flagBits)
d[bindToDevice] = n
}
@@ -353,7 +395,7 @@ func (s *PortManager) ReleasePort(networks []tcpip.NetworkProtocolNumber, transp
s.mu.Lock()
defer s.mu.Unlock()
- flagBits := flags.bits()
+ flagBits := flags.Bits()
for _, network := range networks {
desc := portDescriptor{network, transport, port}
@@ -368,7 +410,7 @@ func (s *PortManager) ReleasePort(networks []tcpip.NetworkProtocolNumber, transp
}
n.refs[flagBits]--
d[bindToDevice] = n
- if n.refs == [nextFlag]int{} {
+ if n.TotalRefs() == 0 {
delete(d, bindToDevice)
}
if len(d) == 0 {
--
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