hop-2012/server/relay.c

/* Copyright (C) 2010, 2011 Tony Garnock-Jones. All rights reserved. */

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>

#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netdb.h>
#include <netinet/in.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <time.h>
#include <sys/time.h>

#include <assert.h>

typedef unsigned char u_char;
#include <event.h>

#include "cmsg_private.h"
#include "harness.h"
#include "relay.h"
#include "net.h"
#include "ref.h"
#include "sexp.h"
#include "sexpio.h"
#include "hashtable.h"
#include "node.h"

#define WANT_MESSAGE_TRACE 0

typedef struct relay_extension_t_ {
  struct sockaddr_in peername;
  char peername_str[256];
  int fd;
  IOHandle *outh;
} relay_extension_t;

static sexp_t *relay_extend(node_t *n, sexp_t *args) {
  /* TODO: outbound connections; args==NULL -> server relay, nonNULL -> outbound. */
  n->extension = calloc(1, sizeof(relay_extension_t));
  return NULL;
}

static void relay_destructor(node_t *n) {
  relay_extension_t *r = n->extension;
  delete_iohandle(r->outh);
  r->outh = NULL;
  if (close(r->fd) == -1) {
    /* log errors as warnings here and keep on trucking */
    warn("Closing file descriptor %d produced errno %d: %s\n",
	 r->fd, errno, strerror(errno));
  }
  free(r);
}

static void relay_handle_message(node_t *n, sexp_t *m) {
  relay_extension_t *r = n->extension;

#if WANT_MESSAGE_TRACE
  info("fd %d <-- ", r->fd);
  sexp_writeln(stderr_h, m);
#endif

  BCHECK(!sexp_write(r->outh, m), "relay_handle_message sexp_write");
}

static node_class_t relay_class = {
  .name = "relay",
  .extend = relay_extend,
  .destroy = relay_destructor,
  .handle_message = relay_handle_message
};

static void send_error(IOHandle *h, char const *message, sexp_t *extra) {
  sexp_t *m = extra;
  m = sexp_cons(sexp_cstring(message), m);
  m = sexp_cons(sexp_cstring("error"), m);
  INCREF(m);

  iohandle_clear_error(h);
  BCHECK(!sexp_write(h, m), "send_error sexp_write");
  DECREF(m, sexp_destructor);
  iohandle_flush(h); /* ignore result here, there's not much we can do with it */
}

static void send_sexp_syntax_error(IOHandle *h, char const *message) {
  char const *url = "http://people.csail.mit.edu/rivest/Sexp.txt";
  send_error(h, message, sexp_cons(sexp_cstring(url), NULL));
}

static void relay_main(node_t *n) {
  relay_extension_t *r = n->extension;
  IOHandle *inh = new_iohandle(r->fd);
  sexp_t *message = NULL; /* held */

  INCREF(n); /* because the caller doesn't hold a ref, and we need to
		drop ours on our death */

  info("Accepted connection from %s on fd %d\n", r->peername_str, r->fd);

  iohandle_write(r->outh, cmsg_cstring_bytes("(3:hop1:0)"));
  ICHECK(iohandle_flush(r->outh), "iohandle_flush greeting");

  //iohandle_settimeout(r->inh, 3, 0);

  while (1) {
    DECREF(message, sexp_destructor);
    message = NULL;
    if (!sexp_read(inh, &message)) goto network_error;
    INCREF(message);

#if WANT_MESSAGE_TRACE
    info("fd %d --> ", r->fd);
    sexp_writeln(stderr_h, message);
#endif

    if (!(sexp_pairp(message) && sexp_stringp(sexp_head(message)))) {
      info("Ill-formed message\n");
      send_error(r->outh, "ill-formed message", NULL);
      goto protocol_error;
    }

    {
      cmsg_bytes_t selector = sexp_data(sexp_head(message));
      sexp_t *args = sexp_tail(message);
      size_t msglen = sexp_length(message);

      /* TODO: have constant atoms for post, subscribe, unsubscribe
	 etc (see also post_node() and the handler in queue.c etc) */

      if (!cmsg_bytes_cmp(selector, cmsg_cstring_bytes("post")) && (msglen == 4)
	  && sexp_stringp(sexp_head(args))) {
	cmsg_bytes_t nodename = sexp_data(sexp_head(args));
	if (!send_node(nodename, sexp_head(sexp_tail(args)))) {
	  warn("Was asked to post to unknown node <<%.*s>>\n", nodename.len, nodename.bytes);
	}
      } else if (!cmsg_bytes_cmp(selector, cmsg_cstring_bytes("subscribe")) && (msglen == 6)
		 && sexp_stringp(sexp_head(args))
		 && sexp_stringp(sexp_head(sexp_tail(sexp_tail(sexp_tail(args)))))
		 && sexp_stringp(sexp_head(sexp_tail(sexp_tail(sexp_tail(sexp_tail(args))))))) {
	sexp_t *filter_sexp = sexp_head(args);
	cmsg_bytes_t filter = sexp_data(filter_sexp);
	sexp_t *reply_sink = sexp_listref(args, 3);
	sexp_t *reply_name = sexp_listref(args, 4);
	if (bind_node(filter, n)) {
	  sexp_t *subok = sexp_cons(sexp_cstring("subscribe-ok"), sexp_cons(filter_sexp, NULL));
	  INCREF(subok);
	  post_node(sexp_data(reply_sink), sexp_data(reply_name), subok, sexp_empty_bytes);
	  DECREF(subok, sexp_destructor);
	} else {
	  warn("Bind failed <<%.*s>>\n", filter.len, filter.bytes);
	}
      } else if (!cmsg_bytes_cmp(selector, cmsg_cstring_bytes("unsubscribe")) && (msglen == 2)
		 && sexp_stringp(sexp_head(args))) {
	sexp_t *id_sexp = sexp_head(args);
	cmsg_bytes_t id = sexp_data(id_sexp);
	if (!unbind_node(id)) {
	  warn("Unbind failed <<%.*s>>\n", id.len, id.bytes);
	}
      } else {
	send_error(r->outh, "message not understood", sexp_cons(message, NULL));
	goto protocol_error;
      }
    }
  }

 network_error:
  if (inh->eof) {
    info("Disconnecting fd %d normally.\n", r->fd);
  } else {
    switch (inh->error_kind) {
      case SEXP_ERROR_OVERFLOW:
	send_sexp_syntax_error(r->outh, "sexp too big");
	break;

      case SEXP_ERROR_SYNTAX:
	send_sexp_syntax_error(r->outh, "sexp syntax error");
	break;

      default:
	warn("Relay handle error 0x%04X on fd %d: %d, %s\n",
	     inh->error_kind, r->fd, inh->error_errno, strerror(inh->error_errno));
	break;
    }
  }

 protocol_error:
  DECREF(message, sexp_destructor);
  delete_iohandle(inh);
  unbind_all_names_for_node(n);
  DECREF(n, node_destructor);
}

void start_relay(struct sockaddr_in const *peername, int fd) {
  node_t *n = new_node(&relay_class, NULL, NULL);
  relay_extension_t *r = n->extension;
  r->peername = *peername;
  endpoint_name(&r->peername, CMSG_BYTES(sizeof(r->peername_str), r->peername_str));
  r->fd = fd;
  r->outh = new_iohandle(r->fd);
  spawn((process_main_t) relay_main, n);
}