From cf978e1531fec77b4998bc0bd583f5fb2e1cf7ea Mon Sep 17 00:00:00 2001
From: Teerapap Changwichukarn <teerapap.c@gmail.com>
Date: Mon, 21 Aug 2023 17:51:07 +0800
Subject: [PATCH] Fix Via header builder to print IPv6 address brackets

According to RFC3261, IPv6 address in host part of the Via header must
be enclosed with brackets ('[' and ']')

Changes in detail
* Enclose the host part of Via header with brackets ('[' and ']') when
  it is IPv6 address
* Add unit tests for IPv6 address case
---
 .../io/pkts/packet/sip/header/ViaHeader.java  | 26 ++++++++++++-
 .../sip/header/impl/ViaHeaderImplTest.java    | 37 +++++++++++++++----
 2 files changed, 54 insertions(+), 9 deletions(-)

diff --git a/pkts-sip/src/main/java/io/pkts/packet/sip/header/ViaHeader.java b/pkts-sip/src/main/java/io/pkts/packet/sip/header/ViaHeader.java
index c0543eeb..84d848cf 100644
--- a/pkts-sip/src/main/java/io/pkts/packet/sip/header/ViaHeader.java
+++ b/pkts-sip/src/main/java/io/pkts/packet/sip/header/ViaHeader.java
@@ -530,11 +530,35 @@ public ViaHeader build() throws SipParseException {
             return new ViaHeaderImpl(via, transport, host, port, params, indexOfBranch, indexOfReceived, indexOfRPort);
         }
 
-        private void transferValue(final Buffer dst) {
+        private boolean isIPv6Address(final Buffer host) throws SipParseException {
+            host.markReaderIndex();
+            try {
+                while (host.hasReadableBytes()) {
+                    final byte b = host.readByte();
+                    if (b == SipParser.COLON) {
+                        return true;
+                    }
+                }
+                return false; // no colon found so it is not IPv6 address
+            } catch (IOException ex) {
+                throw new SipParseException(host.getReaderIndex(), "Fail to read host buffer", ex);
+            } finally {
+                host.resetReaderIndex();
+            }
+        }
+
+        private void transferValue(final Buffer dst) throws SipParseException {
             SipParser.SIP2_0_SLASH.getBytes(0, dst);
             this.transport.toUpperCaseBuffer().getBytes(0, dst);
             dst.write(SipParser.SP);
+            boolean isHostIPv6 = isIPv6Address(this.host);
+            if (isHostIPv6) {
+                dst.write(SipParser.LSBRACKET);
+            }
             this.host.getBytes(0, dst);
+            if (isHostIPv6) {
+                dst.write(SipParser.RSBRACKET);
+            }
             if (this.port != -1) {
                 dst.write(SipParser.COLON);
                 dst.writeAsString(this.port);
diff --git a/pkts-sip/src/test/java/io/pkts/packet/sip/header/impl/ViaHeaderImplTest.java b/pkts-sip/src/test/java/io/pkts/packet/sip/header/impl/ViaHeaderImplTest.java
index 392029f4..8beba0e2 100644
--- a/pkts-sip/src/test/java/io/pkts/packet/sip/header/impl/ViaHeaderImplTest.java
+++ b/pkts-sip/src/test/java/io/pkts/packet/sip/header/impl/ViaHeaderImplTest.java
@@ -20,15 +20,24 @@ public class ViaHeaderImplTest {
 
     @Test
     public void testBuildFromScratch() throws Exception {
-        final ViaHeader via = ViaHeader.withHost("pkts.io")
-                .withBranch("hello")
-                .withPort(5088)
-                .build();
+        // domain name
+        assertViaBuild("pkts.io", 5088, "hello", "Via: SIP/2.0/UDP pkts.io:5088;branch=hello");
+
+        // IPv4 address
+        assertViaBuild("127.0.0.1", 5088, "hello", "Via: SIP/2.0/UDP 127.0.0.1:5088;branch=hello");
+
+        // IPv6 address
+        final String[] ipv6Array = new String[]{
+                "2001:0db8:85a3:0042:1000:8a2e:0370:7334" /* full form */,
+                "ef82::1a12:1234:1b12",  /* Rule 1 - zero compression rule */
+                "1234:fd2:5621:1:89:0:0:4500", /* Rule 2 - leading zero compression rule */
+                "2001:1234::1b12:0:0:1a13", /* Rule 3 - zero is compressed at only one junction */
+        };
+
+        for (String ipv6 : ipv6Array) {
+            assertViaBuild(ipv6, 5088, "hello", "Via: SIP/2.0/UDP [" + ipv6 + "]:5088;branch=hello");
+        }
 
-        assertThat(via.getPort(), is(5088));
-        assertThat(via.getBranch().toString(), is("hello"));
-        assertThat(via.getHost().toString(), is("pkts.io"));
-        assertThat(via.toString(), is("Via: SIP/2.0/UDP pkts.io:5088;branch=hello"));
     }
 
     @Test
@@ -136,6 +145,18 @@ public void testSetParam() throws Exception {
 
     }
 
+    private void assertViaBuild(String host, int port, String branch, String expectedOutput) {
+        final ViaHeader via = ViaHeader.withHost(host)
+                .withBranch(branch)
+                .withPort(port)
+                .build();
+
+        assertThat(via.getPort(), is(port));
+        assertThat(via.getBranch().toString(), is(branch));
+        assertThat(via.getHost().toString(), is(host));
+        assertThat(via.toString(), is(expectedOutput));
+    }
+
     private void assertViaRport(final String toParse, final int port) throws Exception {
         final ViaHeader via = ViaHeader.frame(Buffers.wrap(toParse)).copy().withRPort(port).build();
         assertThat(via.getRPort(), is(port));