Implement a simple proxy server

servers/proxy/build.mk

@@ -0,0 +1 @@
+objs-y += main.o

servers/proxy/main.c

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+#include <libs/common/message.h>
+#include <libs/common/print.h>
+#include <libs/common/string.h>
+#include <libs/user/ipc.h>
+
+int main(void) {
+    // Find {tcpip, echo} server.
+    task_t tcpip_server = ipc_lookup("tcpip");
+    task_t echo_server = ipc_lookup("echo");
+
+    // Listen on port 80.
+    struct message m;
+    m.type = TCPIP_LISTEN_MSG;
+    m.tcpip_listen.listen_port = 80;
+    ASSERT_OK(ipc_call(tcpip_server, &m));
+
+    while(true) {
+        ASSERT_OK(ipc_recv(IPC_ANY, &m));
+
+        DBG(
+            "received message from #%d: %s (%x)", m.src,
+            msgtype2str(m.type),
+            m.type
+        );
+
+        switch(m.type) {
+            case TCPIP_CLOSED_MSG: {
+                // Destroy socket.
+                m.type = TCPIP_DESTROY_MSG;
+                m.tcpip_destroy.sock = m.tcpip_closed.sock;
+                ASSERT_OK(ipc_call(tcpip_server, &m));
+                break;
+            }
+            case TCPIP_DATA_MSG: {
+                int sock = m.tcpip_data.sock;
+
+                // Read the received data.
+                m.type = TCPIP_READ_MSG;
+                m.tcpip_read.sock = sock;
+                ASSERT_OK(ipc_call(tcpip_server, &m));
+
+                char data[1024];
+                size_t data_len = m.tcpip_read_reply.data_len;
+                memcpy(data, m.tcpip_read_reply.data, data_len);
+
+                DBG("received data (%u bytes) from socket %d", data_len, sock);
+
+                // Relay to the echo server.
+                m.type = ECHO_MSG;
+                m.echo.data_len = data_len;
+                memcpy(m.echo.data, data, data_len);
+                ASSERT_OK(ipc_call(echo_server, &m));
+                ASSERT(m.echo_reply.data_len == data_len);
+
+                // Replay to the client.
+                memcpy(data, m.echo_reply.data, data_len);
+                m.type = TCPIP_WRITE_MSG;
+                m.tcpip_write.sock = sock;
+                memcpy(m.tcpip_write.data, data, data_len);
+                m.tcpip_write.data_len = data_len;
+                ASSERT_OK(ipc_call(tcpip_server, &m));
+                break;
+            }
+        }
+    }
+}