[vpp]: Add sr0 interface for VPP. (sonic-net#24359)

SONiC VPP has support for SRv6, but the sr0 interface is needed for it to work; added here in 202411: Azure/sonic-buildimage-msft#517. A commit to master has comments requesting it to be enabled per platform: sonic-net#24084. Adding this change so that for VPP it is enabled and can allow sonic-mgmt tests for srv6 to be run with Sonic-VPP.

Author: dypet

dockers/docker-fpm-frr/docker_init.sh

@@ -99,6 +99,18 @@ fi
 
 chown -R frr:frr /etc/frr/
 
+# Create sr0 interface for SRv6 support
+SONIC_ASIC_TYPE=$(sed -n 's/^asic_type:[[:space:]]*//p' /etc/sonic/sonic_version.yml)
+if [ "$SONIC_ASIC_TYPE" == "vpp" ]; then
+    if ! ip link show sr0 > /dev/null 2>&1; then
+        echo "Interface sr0 does not exist. Creating sr0..."
+        ip link add sr0 type dummy || true
+    else
+        echo "Interface sr0 already exists."
+    fi
+    ip link set sr0 up || true
+fi
+
 chown root:root /usr/sbin/bgp-isolate
 chmod 0755 /usr/sbin/bgp-isolate