use more appropriate ant target

Update read buffer offset.  Fixes occasional mangling, trac ticket 2765

See merge request zlatinb/i2p.i2p!1

Dockerfile

@@ -1,27 +1,36 @@
 FROM jlesage/baseimage:alpine-3.10-glibc
+
+### CHANGE THIS!!! #####
+# This is the port I2P will listen on for incoming connections.
+# If you leave it as 12345 others will be able to guess you are
+# running a docker image!
+ENV I2NP_PORT=12345
+########################
+
+
 ENV APP_HOME="/i2p"
 
 WORKDIR /tmp/build
 COPY . .
 
-# Build package
-RUN add-pkg openjdk8-jre
-RUN add-pkg --virtual build-base gettext tar bzip2 apache-ant openjdk8
-RUN echo "noExe=true" >> build.properties
-RUN ant clean pkg
-RUN del-pkg build-base gettext tar bzip2 apache-ant openjdk8
 
-# "install" files
-RUN mkdir -p ${APP_HOME}
-RUN mv pkg-temp/* ${APP_HOME}
+RUN add-pkg openjdk8-jre \
+    && add-pkg --virtual build-base gettext tar bzip2 apache-ant openjdk8 \
+    && ant clean preppkg-linux-only \
+    && del-pkg build-base gettext tar bzip2 apache-ant openjdk8 \
+    && mkdir -p ${APP_HOME} \
+    && mv pkg-temp/* ${APP_HOME}
+
 
 # "install" i2p by copying over installed files
 COPY docker/rootfs/ /
+RUN cat /i2p/router.config.template | sed "s/I2NP_PORT/${I2NP_PORT}/g" > /i2p/router.config
 
-# Mount home
+# Mount home and snark
 VOLUME ["${APP_HOME}/.i2p"]
+VOLUME ["/i2psnark"]
 
-EXPOSE 7654 7656 7657 7658 4444 6668 8998 7659 7660 4445
+EXPOSE 7654 7656 7657 7658 4444 6668 8998 7659 7660 4445 ${I2NP_PORT}
 
 # Metadata.
 LABEL \

docker/rootfs/i2p/i2psnark.config

@@ -0,0 +1,12 @@
+# NOTE: This I2P config file must use UTF-8 encoding
+#
+# If you have a 'split' directory installation, with configuration
+# files in ~/.i2p (Linux), %LOCALAPPDATA%\I2P (Windows),
+# or /Users/(user)/Library/Application Support/i2p (Mac), be sure to
+# edit the file in the configuration directory, NOT the install directory.
+# When running as a Linux daemon, the configuration directory is /var/lib/i2p
+# and the install directory is /usr/share/i2p .
+# When running as a Windows service, the configuration directory is \ProgramData\i2p
+# and the install directory is \Program Files\i2p .
+#
+i2psnark.dir=/i2psnark

docker/rootfs/i2p/router.config.template

@@ -0,0 +1,4 @@
+router.updateDisabled=true
+i2np.ntcp.port=I2NP_PORT
+i2np.udp.port=I2NP_PORT
+i2np.udp.internalPort=I2NP_PORT