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[meshnet] Manage system-level kernel and link tunables for packet performance #734

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[meshnet] Manage system-level kernel and link tunables for packet performance #734

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2 changes: 2 additions & 0 deletions third_party/meshnet/daemon/main.go
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,8 @@ func main() {
}
defer cni.Cleanup()

wireutil.TuneSystem()

@bstoll bstoll Aug 13, 2026

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Can we move all of this to documentation instead (explaining why we are changing these things?) I think these kind of settings are really up to the user to implement - we should not be forcing tuning settings in code like this. We could make changes to cloudbuild/internal.pkr.hcl and cloudbuild/external.pkr.hcl if there are changes that will improve performance measurably in the VM images.

I don't think many of these changes are relevant or helping: ARP/ND cache GC thresh doesn't do much, rp_filter is not a performance knob, ipv6/route/max_size should not be changed, default/router_solicitations , accept_dad, mld_max_msf, and igmp_max_memberships don't do much in the host OS and are not going to change performance. RLIMIT_NOFILE seems like its changing something for a limit we've never hit?

The txqueuelen, netdev_max_backlog, and [wr]mem_(default|max) I can imagine are going to affect performance. I think setting the initial window size to 16MB is a little excessive, but increasing the max seems OK.

@kraney kraney Aug 17, 2026

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I may have gotten overzealous trying to clear the last packet drops. Let me revisit


isDebug := flag.Bool("d", false, "enable degugging")
grpcPort, err := strconv.Atoi(os.Getenv("GRPC_PORT"))
if err != nil || grpcPort == 0 {
Expand Down
15 changes: 15 additions & 0 deletions third_party/meshnet/daemon/vxlan/vxlan.go
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Expand Up @@ -13,6 +13,7 @@ import (
"github.com/vishvananda/netlink"

mpb "github.com/openconfig/kne/third_party/meshnet/daemon/proto/meshnet/v1beta1"
"github.com/openconfig/kne/third_party/meshnet/utils/wireutil"
)

var vxLanOvrlyLogger *log.Entry = nil
Expand Down Expand Up @@ -107,6 +108,20 @@ func CreateOrUpdate(v *mpb.RemotePod) error {
}
}

// Tune txqueuelen inside the container netns (configurable via LINK_TXQUEUELEN)
if podNs, err := ns.GetNS(veth.NsName); err == nil {
_ = podNs.Do(func(_ ns.NetNS) error {
if link, err := netlink.LinkByName(veth.LinkName); err == nil {
txqLen := wireutil.GetLinkTxQLen()
if err := netlink.LinkSetTxQLen(link, txqLen); err != nil {
vxLanOvrlyLogger.Warnf("failed to set txqueuelen %d on %s inside %s: %v", txqLen, veth.LinkName, veth.NsName, err)
}
}
return nil
})
podNs.Close()
}

return nil
}

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62 changes: 62 additions & 0 deletions third_party/meshnet/utils/wireutil/sys_tune.go
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Expand Up @@ -3,6 +3,9 @@ package wireutil
import (
"os"
"strconv"

log "github.com/sirupsen/logrus"
"golang.org/x/sys/unix"
)

// GetEnvInt reads an integer environment variable with a default fallback value if unset or invalid.
Expand All @@ -14,3 +17,62 @@ func GetEnvInt(key string, defaultVal int) int {
}
return defaultVal
}

func getEnvString(key string, defaultVal string) string {
if valStr := os.Getenv(key); valStr != "" {
return valStr
}
return defaultVal
}

// GetLinkTxQLen returns the configured link txqueuelen (default 10000, configurable via LINK_TXQUEUELEN).
func GetLinkTxQLen() int {
return GetEnvInt("LINK_TXQUEUELEN", 10000)
}

// TuneSystem configures global OS sysctl tunables (backlog, buffers, ARP/neighbor GC thresholds,
// multicast group limits, rp_filter, and IPv6 startup behavior) and RLIMIT_NOFILE for high-density,
// high-throughput network topologies. Values can be customized via environment variables.
func TuneSystem() {
// 1. Increase max open file descriptors for daemon (rlimit)
noFileLimit := GetEnvInt("RLIMIT_NOFILE", 1048576)
var rlim unix.Rlimit
rlim.Max = uint64(noFileLimit)
rlim.Cur = uint64(noFileLimit)
if err := unix.Setrlimit(unix.RLIMIT_NOFILE, &rlim); err != nil {
log.Warnf("TuneSystem: failed to set RLIMIT_NOFILE to %d: %v", noFileLimit, err)
} else {
log.Infof("TuneSystem: successfully set RLIMIT_NOFILE to %d", noFileLimit)
}

// 2. Sysctl kernel tunables for network device backlog, buffer limits, ARP/neighbor GC thresholds,
// multicast memberships, reverse path filtering, and IPv6 DAD/RS startup tuning.
sysctls := map[string]string{
"/proc/sys/net/core/netdev_max_backlog": getEnvString("NETDEV_MAX_BACKLOG", "10000"),
"/proc/sys/net/core/rmem_max": getEnvString("RMEM_MAX", "16777216"),
"/proc/sys/net/core/wmem_max": getEnvString("WMEM_MAX", "16777216"),
"/proc/sys/net/core/rmem_default": getEnvString("RMEM_DEFAULT", "16777216"),
"/proc/sys/net/core/wmem_default": getEnvString("WMEM_DEFAULT", "16777216"),
"/proc/sys/net/ipv4/neigh/default/gc_thresh1": getEnvString("ARP_GC_THRESH1", "1024"),
"/proc/sys/net/ipv4/neigh/default/gc_thresh2": getEnvString("ARP_GC_THRESH2", "4096"),
"/proc/sys/net/ipv4/neigh/default/gc_thresh3": getEnvString("ARP_GC_THRESH3", "8192"),
"/proc/sys/net/ipv6/neigh/default/gc_thresh1": getEnvString("ARP_GC_THRESH1", "1024"),
"/proc/sys/net/ipv6/neigh/default/gc_thresh2": getEnvString("ARP_GC_THRESH2", "4096"),
"/proc/sys/net/ipv6/neigh/default/gc_thresh3": getEnvString("ARP_GC_THRESH3", "8192"),
"/proc/sys/net/ipv4/igmp_max_memberships": getEnvString("IGMP_MAX_MEMBERSHIPS", "10000"),
"/proc/sys/net/ipv6/mld_max_msf": getEnvString("MLD_MAX_MSF", "4096"),
"/proc/sys/net/ipv4/conf/all/rp_filter": getEnvString("RP_FILTER", "2"),
"/proc/sys/net/ipv4/conf/default/rp_filter": getEnvString("RP_FILTER", "2"),
"/proc/sys/net/ipv6/conf/default/accept_dad": getEnvString("IPV6_ACCEPT_DAD", "0"),
"/proc/sys/net/ipv6/conf/default/router_solicitations": getEnvString("IPV6_ROUTER_SOLICITATIONS", "0"),
"/proc/sys/net/ipv6/route/max_size": getEnvString("IPV6_ROUTE_MAX_SIZE", "1048576"),
}

for path, val := range sysctls {
if err := os.WriteFile(path, []byte(val), 0644); err != nil {
log.Warnf("TuneSystem: failed to write %s to %s: %v", val, path, err)
} else {
log.Infof("TuneSystem: set %s = %s", path, val)
}
}
}
6 changes: 6 additions & 0 deletions third_party/meshnet/utils/wireutil/tap.go
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Expand Up @@ -62,6 +62,12 @@ func CreateOrAttachTAP(podNsPath string, ifName string, ipCIDR string) (*os.File
return fmt.Errorf("failed to find link %s inside netns %s: %w", ifName, podNsPath, err)
}

// Increase txqueuelen for high-throughput packet processing (configurable via LINK_TXQUEUELEN)
txqLen := GetLinkTxQLen()
if err := netlink.LinkSetTxQLen(link, txqLen); err != nil {
log.Warnf("CreateOrAttachTAP: failed to set txqueuelen %d on %s in netns %s: %v", txqLen, ifName, podNsPath, err)
}

if err := netlink.LinkSetUp(link); err != nil {
unix.Close(fd)
return fmt.Errorf("failed to set %s UP in netns %s: %w", ifName, podNsPath, err)
Expand Down
6 changes: 6 additions & 0 deletions third_party/meshnet/utils/wireutil/veth.go
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Expand Up @@ -173,6 +173,12 @@ func ConfigurePodLinks(podNsPath string, links []PodLinkConfig) error {
}
}

// Increase txqueuelen for high-throughput packet processing (configurable via LINK_TXQUEUELEN)
txqLen := GetLinkTxQLen()
if err := netlink.LinkSetTxQLen(link, txqLen); err != nil {
log.Warnf("ConfigurePodLinks: failed to set txqueuelen %d on %s inside %s: %v", txqLen, cfg.LocalIntf, podNsPath, err)
}

if err := netlink.LinkSetUp(link); err != nil {
return fmt.Errorf("failed to set %s UP inside %s: %w", cfg.LocalIntf, podNsPath, err)
}
Expand Down
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