pkg/meta/bandwidth: increase IfbDeviceName size

* Increase entroy from 2 bytes to 7 bytes to prevent collisions
* Extract common library function for hash with prefix
* Refactor portmap plugin to use library function

fixes #347

Co-authored-by: Cameron Moreau <cmoreau@pivotal.io>
Co-authored-by: Mikael Manukyan <mmanukyan@pivotal.io>

pkg/utils/utils_test.go

@@ -15,37 +15,151 @@
 package utils
 
 import (
+	"fmt"
+	"strings"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 )
 
 var _ = Describe("Utils", func() {
-	It("must format a short name", func() {
-		chain := FormatChainName("test", "1234")
-		Expect(len(chain)).To(Equal(maxChainLength))
-		Expect(chain).To(Equal("CNI-2bbe0c48b91a7d1b8a6753a8"))
+	Describe("FormatChainName", func() {
+		It("must format a short name", func() {
+			chain := FormatChainName("test", "1234")
+			Expect(len(chain)).To(Equal(maxChainLength))
+			Expect(chain).To(Equal("CNI-2bbe0c48b91a7d1b8a6753a8"))
+		})
+
+		It("must truncate a long name", func() {
+			chain := FormatChainName("testalongnamethatdoesnotmakesense", "1234")
+			Expect(len(chain)).To(Equal(maxChainLength))
+			Expect(chain).To(Equal("CNI-374f33fe84ab0ed84dcdebe3"))
+		})
+
+		It("must be predictable", func() {
+			chain1 := FormatChainName("testalongnamethatdoesnotmakesense", "1234")
+			chain2 := FormatChainName("testalongnamethatdoesnotmakesense", "1234")
+			Expect(len(chain1)).To(Equal(maxChainLength))
+			Expect(len(chain2)).To(Equal(maxChainLength))
+			Expect(chain1).To(Equal(chain2))
+		})
+
+		It("must change when a character changes", func() {
+			chain1 := FormatChainName("testalongnamethatdoesnotmakesense", "1234")
+			chain2 := FormatChainName("testalongnamethatdoesnotmakesense", "1235")
+			Expect(len(chain1)).To(Equal(maxChainLength))
+			Expect(len(chain2)).To(Equal(maxChainLength))
+			Expect(chain1).To(Equal("CNI-374f33fe84ab0ed84dcdebe3"))
+			Expect(chain1).NotTo(Equal(chain2))
+		})
 	})
 
-	It("must truncate a long name", func() {
-		chain := FormatChainName("testalongnamethatdoesnotmakesense", "1234")
-		Expect(len(chain)).To(Equal(maxChainLength))
-		Expect(chain).To(Equal("CNI-374f33fe84ab0ed84dcdebe3"))
+	Describe("MustFormatChainNameWithPrefix", func() {
+		It("generates a chain name with a prefix", func() {
+			chain := MustFormatChainNameWithPrefix("test", "1234", "PREFIX-")
+			Expect(len(chain)).To(Equal(maxChainLength))
+			Expect(chain).To(Equal("CNI-PREFIX-2bbe0c48b91a7d1b8"))
+		})
+
+		It("must format a short name", func() {
+			chain := MustFormatChainNameWithPrefix("test", "1234", "PREFIX-")
+			Expect(len(chain)).To(Equal(maxChainLength))
+			Expect(chain).To(Equal("CNI-PREFIX-2bbe0c48b91a7d1b8"))
+		})
+
+		It("must truncate a long name", func() {
+			chain := MustFormatChainNameWithPrefix("testalongnamethatdoesnotmakesense", "1234", "PREFIX-")
+			Expect(len(chain)).To(Equal(maxChainLength))
+			Expect(chain).To(Equal("CNI-PREFIX-374f33fe84ab0ed84"))
+		})
+
+		It("must be predictable", func() {
+			chain1 := MustFormatChainNameWithPrefix("testalongnamethatdoesnotmakesense", "1234", "PREFIX-")
+			chain2 := MustFormatChainNameWithPrefix("testalongnamethatdoesnotmakesense", "1234", "PREFIX-")
+			Expect(len(chain1)).To(Equal(maxChainLength))
+			Expect(len(chain2)).To(Equal(maxChainLength))
+			Expect(chain1).To(Equal(chain2))
+		})
+
+		It("must change when a character changes", func() {
+			chain1 := MustFormatChainNameWithPrefix("testalongnamethatdoesnotmakesense", "1234", "PREFIX-")
+			chain2 := MustFormatChainNameWithPrefix("testalongnamethatdoesnotmakesense", "1235", "PREFIX-")
+			Expect(len(chain1)).To(Equal(maxChainLength))
+			Expect(len(chain2)).To(Equal(maxChainLength))
+			Expect(chain1).To(Equal("CNI-PREFIX-374f33fe84ab0ed84"))
+			Expect(chain1).NotTo(Equal(chain2))
+		})
+
+		It("panics when prefix is too large", func() {
+			longPrefix := strings.Repeat("PREFIX-", 4)
+			Expect(func() {
+				MustFormatChainNameWithPrefix("test", "1234", longPrefix)
+			}).To(Panic())
+		})
 	})
 
-	It("must be predictable", func() {
-		chain1 := FormatChainName("testalongnamethatdoesnotmakesense", "1234")
-		chain2 := FormatChainName("testalongnamethatdoesnotmakesense", "1234")
-		Expect(len(chain1)).To(Equal(maxChainLength))
-		Expect(len(chain2)).To(Equal(maxChainLength))
-		Expect(chain1).To(Equal(chain2))
+	Describe("MustFormatHashWithPrefix", func() {
+		It("always returns a string with the given prefix", func() {
+			Expect(MustFormatHashWithPrefix(10, "AAA", "some string")).To(HavePrefix("AAA"))
+			Expect(MustFormatHashWithPrefix(10, "foo", "some string")).To(HavePrefix("foo"))
+			Expect(MustFormatHashWithPrefix(10, "bar", "some string")).To(HavePrefix("bar"))
+		})
+
+		It("always returns a string of the given length", func() {
+			Expect(MustFormatHashWithPrefix(10, "AAA", "some string")).To(HaveLen(10))
+			Expect(MustFormatHashWithPrefix(15, "AAA", "some string")).To(HaveLen(15))
+			Expect(MustFormatHashWithPrefix(5, "AAA", "some string")).To(HaveLen(5))
+		})
+
+		It("is deterministic", func() {
+			val1 := MustFormatHashWithPrefix(10, "AAA", "some string")
+			val2 := MustFormatHashWithPrefix(10, "AAA", "some string")
+			val3 := MustFormatHashWithPrefix(10, "AAA", "some string")
+			Expect(val1).To(Equal(val2))
+			Expect(val1).To(Equal(val3))
+		})
+
+		It("is (nearly) perfect (injective function)", func() {
+			hashes := map[string]int{}
+
+			for i := 0; i < 1000; i++ {
+				name := fmt.Sprintf("string %d", i)
+				hashes[MustFormatHashWithPrefix(8, "", name)]++
+			}
+
+			for key, count := range hashes {
+				Expect(count).To(Equal(1), "for key "+key+" got non-unique correspondence")
+			}
+		})
+
+		assertPanicWith := func(f func(), expectedErrorMessage string) {
+			defer func() {
+				Expect(recover()).To(Equal(expectedErrorMessage))
+			}()
+			f()
+			Fail("function should have panicked but did not")
+		}
+
+		It("panics when prefix is longer than the length", func() {
+			assertPanicWith(
+				func() { MustFormatHashWithPrefix(3, "AAA", "some string") },
+				"invalid length",
+			)
+		})
+
+		It("panics when length is not positive", func() {
+			assertPanicWith(
+				func() { MustFormatHashWithPrefix(0, "", "some string") },
+				"invalid length",
+			)
+		})
+
+		It("panics when length is larger than MaxLen", func() {
+			assertPanicWith(
+				func() { MustFormatHashWithPrefix(MaxHashLen+1, "", "some string") },
+				"invalid length",
+			)
+		})
 	})
 
-	It("must change when a character changes", func() {
-		chain1 := FormatChainName("testalongnamethatdoesnotmakesense", "1234")
-		chain2 := FormatChainName("testalongnamethatdoesnotmakesense", "1235")
-		Expect(len(chain1)).To(Equal(maxChainLength))
-		Expect(len(chain2)).To(Equal(maxChainLength))
-		Expect(chain1).To(Equal("CNI-374f33fe84ab0ed84dcdebe3"))
-		Expect(chain1).NotTo(Equal(chain2))
-	})
 })