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fix[vAccel]: optimized hash function in idToGuestCID to reduce collisions #895

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fix[vAccel]: optimized hash function in idToGuestCID to reduce collisions #895

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8cf76f1
fix[vAccel]: modified idToGuestCID function to use hash/fnv hashing
Cicada1107 Aug 3, 2026
2d81418
refactor[vAccel]: updated vaccel_test to account for new CIDs
Cicada1107 Aug 3, 2026
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14 changes: 7 additions & 7 deletions pkg/unikontainers/vaccel.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@ package unikontainers
import (
"errors"
"fmt"
"hash/fnv"
"regexp"

"github.com/opencontainers/runtime-spec/specs-go"
Expand All @@ -30,14 +31,13 @@ var ErrVAccelDisabled = errors.New("vaccel is disabled")
// idToGuestCID generates a deterministic guest CID (Context Identifier)
// for vsock communication based on a container or VM ID.
func idToGuestCID(id string) int {
sum := 0
for _, c := range id {
sum += int(c)
}
h := fnv.New32a()
h.Write([]byte(id))
hashVal := h.Sum32()

const minVal = 3
const maxVal = 99
const valRange = maxVal - minVal + 1
val := (sum % valRange) + minVal
// Max uint32 is 4294967295. Range size = 4294967295 - 3 + 1 = 4294967293
val := int((hashVal % 4294967293) + minVal)

return val
}
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14 changes: 12 additions & 2 deletions pkg/unikontainers/vaccel_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -30,12 +30,22 @@ func TestIdToGuestCID(t *testing.T) {
{
name: "empty string",
id: "",
expectedCID: 3,
expectedCID: 2166136264,
},
{
name: "simple id",
id: "container123",
expectedCID: 49,
expectedCID: 1588278395,
},
{
name: "anagram id 1",
id: "abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789",
expectedCID: 4118960264,
},
{
name: "anagram id 2",
id: "9876543210fedcba9876543210fedcba9876543210fedcba9876543210fedcba",
expectedCID: 1919582536,
},
}

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