Re: [Qemu-devel] [PATCH v2 3/3] Fix address handling in inet_nonblocking_connect

[Markus Armbruster <armbru@redhat.com>]

Orit Wasserman <owasserm@redhat.com> writes:

> getaddrinfo can give us a list of addresses, but we only try to
> connect to the first one. If that fails we never proceed to
> the next one.  This is common on desktop setups that often have ipv6
> configured but not actually working.
>
> To fix this make inet_connect_nonblocking retry connection with a different
> address.
> callers on inet_nonblocking_connect register a callback function that will
> be called when connect opertion completes, in case of failure the fd will have
> a negative value
>
> Signed-off-by: Orit Wasserman <owasserm@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  migration-tcp.c |   29 +++-------
>  qemu-sockets.c  |  169 +++++++++++++++++++++++++++++++++++++++++--------------
>  qemu_socket.h   |    9 ++-
>  3 files changed, 142 insertions(+), 65 deletions(-)
>
> diff --git a/migration-tcp.c b/migration-tcp.c
> index 7f6ad98..cadea36 100644
> --- a/migration-tcp.c
> +++ b/migration-tcp.c
> @@ -53,29 +53,18 @@ static int tcp_close(MigrationState *s)
>      return r;
>  }
>  
> -static void tcp_wait_for_connect(void *opaque)
> +static void tcp_wait_for_connect(int fd, void *opaque)
>  {
>      MigrationState *s = opaque;
> -    int val, ret;
> -    socklen_t valsize = sizeof(val);
>  
> -    DPRINTF("connect completed\n");
> -    do {
> -        ret = getsockopt(s->fd, SOL_SOCKET, SO_ERROR, (void *) &val, &valsize);
> -    } while (ret == -1 && (socket_error()) == EINTR);
> -
> -    if (ret < 0) {
> +    if (fd < 0) {
> +        DPRINTF("migrate connect error\n");
> +        s->fd = -1;
>          migrate_fd_error(s);
> -        return;
> -    }
> -
> -    qemu_set_fd_handler2(s->fd, NULL, NULL, NULL, NULL);
> -
> -    if (val == 0)
> +    } else {
> +        DPRINTF("migrate connect success\n");
> +        s->fd = fd;
>          migrate_fd_connect(s);
> -    else {
> -        DPRINTF("error connecting %d\n", val);
> -        migrate_fd_error(s);
>      }
>  }
>  
> @@ -88,7 +77,8 @@ int tcp_start_outgoing_migration(MigrationState *s, const char *host_port,
>      s->write = socket_write;
>      s->close = tcp_close;
>  
> -    s->fd = inet_nonblocking_connect(host_port, &in_progress, errp);
> +    s->fd = inet_nonblocking_connect(host_port, tcp_wait_for_connect, s,
> +                                     &in_progress, errp);
>      if (error_is_set(errp)) {
>          migrate_fd_error(s);
>          return -1;
> @@ -96,7 +86,6 @@ int tcp_start_outgoing_migration(MigrationState *s, const char *host_port,
>  
>      if (in_progress) {
>          DPRINTF("connect in progress\n");
> -        qemu_set_fd_handler2(s->fd, NULL, NULL, tcp_wait_for_connect, s);
>      } else {
>          migrate_fd_connect(s);
>      }
> diff --git a/qemu-sockets.c b/qemu-sockets.c
> index 4f5eca8..f5d64c8 100644
> --- a/qemu-sockets.c
> +++ b/qemu-sockets.c
> @@ -24,6 +24,7 @@
>  
>  #include "qemu_socket.h"
>  #include "qemu-common.h" /* for qemu_isdigit */
> +#include "main-loop.h"
>  
>  #ifndef AI_ADDRCONFIG
>  # define AI_ADDRCONFIG 0
> @@ -209,41 +210,27 @@ listen:
>      return slisten;
>  }
>  
> -static struct addrinfo *inet_parse_connect_opts(QemuOpts *opts, Error **errp)
> -{
> -    struct addrinfo ai, *res;
> -    int rc;
> -    const char *addr;
> -    const char *port;
> -
> -    memset(&ai,0, sizeof(ai));
> -    ai.ai_flags = AI_CANONNAME | AI_ADDRCONFIG;
> -    ai.ai_family = PF_UNSPEC;
> -    ai.ai_socktype = SOCK_STREAM;
> -
> -    addr = qemu_opt_get(opts, "host");
> -    port = qemu_opt_get(opts, "port");
> -    if (addr == NULL || port == NULL) {
> -        fprintf(stderr,
> -                "inet_parse_connect_opts: host and/or port not specified\n");
> -        error_set(errp, QERR_SOCKET_CREATE_FAILED);
> -        return NULL;
> -    }
> -
> -    if (qemu_opt_get_bool(opts, "ipv4", 0))
> -        ai.ai_family = PF_INET;
> -    if (qemu_opt_get_bool(opts, "ipv6", 0))
> -        ai.ai_family = PF_INET6;
> +#ifdef _WIN32
> +#define QEMU_SOCKET_RC_INPROGRESS(rc) \
> +    ((rc) == -EINPROGRESS || rc == -EWOULDBLOCK || rc == -WSAEALREADY)
> +#else
> +#define QEMU_SOCKET_RC_INPROGRESS(rc) \
> +    ((rc) == -EINPROGRESS)
> +#endif
>  
> -    /* lookup */
> -    if (0 != (rc = getaddrinfo(addr, port, &ai, &res))) {
> -        fprintf(stderr,"getaddrinfo(%s,%s): %s\n", addr, port,
> -                gai_strerror(rc));
> -        error_set(errp, QERR_SOCKET_CREATE_FAILED);
> -        return NULL;
> -    }
> -    return res;
> -}

inet_parse_connect_opts() is only moved, not changed, I think.  I like
to keep code motion well away from code changes (separate patch) to
facilitate review.

> +/* Struct to store connect state for non blocking connect */
> +typedef struct ConnectState {
> +    int fd;
> +    struct addrinfo *addr_list;
> +    struct addrinfo *current_addr;
> +    ConnectHandler *callback;
> +    void *opaque;
> +    Error *errp;
> +} ConnectState;
> +
> +static ConnectState connect_state = {
> +    .fd = -1,
> +};

Why does a single connect_state suffice?

>  
>  #ifdef _WIN32
>  #define QEMU_SOCKET_RC_INPROGRESS(rc) \
> @@ -254,12 +241,17 @@ static struct addrinfo *inet_parse_connect_opts(QemuOpts *opts, Error **errp)
>  #endif
>  
>  static int inet_connect_addr(struct addrinfo *addr, bool block,
> -                             bool *in_progress, Error **errp)
> +                             IOHandler *handler, bool *in_progress,
> +                             Error **errp)

Sure you want a handler parameter?  It's always wait_for_connect()...

>  {
>      char uaddr[INET6_ADDRSTRLEN + 1];
>      char uport[33];
>      int sock, rc;
>  
> +    if (in_progress) {
> +        *in_progress = false;
> +    }
> +
>      if (getnameinfo((struct sockaddr *)addr->ai_addr, addr->ai_addrlen,
>                      uaddr, INET6_ADDRSTRLEN, uport, 32,
>                      NI_NUMERICHOST | NI_NUMERICSERV)) {
> @@ -285,6 +277,8 @@ static int inet_connect_addr(struct addrinfo *addr, bool block,
>      } while (rc == -EINTR);
>  
>      if (!block && QEMU_SOCKET_RC_INPROGRESS(rc)) {
> +        connect_state.fd = sock;
> +        qemu_set_fd_handler2(sock, NULL, NULL, handler, &connect_state);
>          if (in_progress) {
>              *in_progress = true;
>          }
> @@ -295,6 +289,94 @@ static int inet_connect_addr(struct addrinfo *addr, bool block,
>      return sock;
>  }
>  
> +static void wait_for_connect(void *opaque)
> +{
> +    ConnectState *s = opaque;
> +    int val = 0, rc = 0;
> +    socklen_t valsize = sizeof(val);
> +    bool in_progress = false;
> +
> +    do {
> +        rc = getsockopt(s->fd, SOL_SOCKET, SO_ERROR, (void *) &val, &valsize);
> +    } while (rc == -1 && (socket_error()) == EINTR);

Either parenthesize both operands of && or none.  I prefer none.

> +
> +    /* connect succeded */
> +    if (!rc && !val) {
> +        qemu_set_fd_handler2(s->fd, NULL, NULL, NULL, NULL);
> +        freeaddrinfo(s->addr_list);
> +        if (s->callback) {
> +            s->callback(s->fd, s->opaque);
> +        }
> +        return;
> +    }
> +
> +    if (!rc && val) {
> +        rc = -val;
> +    }
> +
> +    qemu_set_fd_handler2(s->fd, NULL, NULL, NULL, NULL);
> +    closesocket(s->fd);
> +    if (s->current_addr != NULL && s->current_addr->ai_next != NULL) {

How can s->current_addr == NULL happen?

> +        s->current_addr = s->current_addr->ai_next;
> +        s->fd = inet_connect_addr(s->current_addr, false, wait_for_connect,
> +                                  &in_progress, &s->errp);

inet_connect_addr() either

1. completes connect (returns valid fd, sets in_progress to false), or

2. starts connect (returns valid fd, sets in_progress to true), or

3. fails (returns -1 and sets in_progress to false).

> +        if (in_progress) {
> +            return;

Case 2.

> +        }
> +    }

To reach this point, we either ran out of addresses (if not entered), or
connect to the current address completed (case 1), or connect failed
(case 3).

> +
> +    qemu_set_fd_handler2(s->fd, NULL, NULL, NULL, NULL);
> +
> +    closesocket(s->fd);
> +    s->fd = rc;
> +    freeaddrinfo(s->addr_list);
> +    /* connect failed */
> +    if (s->callback) {
> +        s->callback(s->fd, s->opaque);
> +    }
> +    return;

Either I'm confused, or this treats completed connect() as failure,
which is wrong.

> +}
> +
> +static struct addrinfo *inet_parse_connect_opts(QemuOpts *opts, Error **errp)
> +{
> +    struct addrinfo ai, *res;
> +    int rc;
> +    const char *addr;
> +    const char *port;
> +
> +    memset(&ai, 0, sizeof(ai));
> +    ai.ai_flags = AI_CANONNAME | AI_ADDRCONFIG;
> +    ai.ai_family = PF_UNSPEC;
> +    ai.ai_socktype = SOCK_STREAM;
> +
> +    addr = qemu_opt_get(opts, "host");
> +    port = qemu_opt_get(opts, "port");
> +    if (addr == NULL || port == NULL) {
> +        fprintf(stderr,
> +                "inet_parse_connect_opts: host and/or port not specified\n");
> +        error_set(errp, QERR_SOCKET_CREATE_FAILED);
> +        return NULL;
> +    }
> +
> +    if (qemu_opt_get_bool(opts, "ipv4", 0)) {
> +        ai.ai_family = PF_INET;
> +    }
> +    if (qemu_opt_get_bool(opts, "ipv6", 0)) {
> +        ai.ai_family = PF_INET6;
> +    }
> +
> +    /* lookup */
> +    rc = getaddrinfo(addr, port, &ai, &res);
> +    if (rc != 0) {
> +        fprintf(stderr, "getaddrinfo(%s,%s): %s\n", addr, port,
> +                gai_strerror(rc));
> +        error_set(errp, QERR_SOCKET_CREATE_FAILED);
> +        return NULL;
> +    }
> +    return res;
> +}
> +
> +
>  int inet_connect_opts(QemuOpts *opts, bool *in_progress, Error **errp)
>  {
>      struct addrinfo *res, *e;
> @@ -306,12 +388,12 @@ int inet_connect_opts(QemuOpts *opts, bool *in_progress, Error **errp)
>          return -1;
>      }
>  
> -    if (in_progress) {
> -        *in_progress = false;
> -    }
> -
>      for (e = res; e != NULL; e = e->ai_next) {
> -        sock = inet_connect_addr(e, block, in_progress, errp);
> +        if (!block) {
> +            connect_state.addr_list = res;
> +            connect_state.current_addr = e;
> +        }
> +        sock = inet_connect_addr(e, block, wait_for_connect, in_progress, errp);
>          if (in_progress && *in_progress) {
>              return sock;
>          } else if (sock >= 0) {
> @@ -534,9 +616,8 @@ int inet_connect(const char *str, Error **errp)
>      return sock;
>  }
>  
> -
> -int inet_nonblocking_connect(const char *str, bool *in_progress,
> -                             Error **errp)
> +int inet_nonblocking_connect(const char *str, ConnectHandler *callback,
> +                             void *opaque, bool *in_progress, Error **errp)
>  {
>      QemuOpts *opts;
>      int sock = -1;
> @@ -544,6 +625,8 @@ int inet_nonblocking_connect(const char *str, bool *in_progress,
>      opts = qemu_opts_create(&dummy_opts, NULL, 0, NULL);
>      if (inet_parse(opts, str) == 0) {
>          qemu_opt_set(opts, "block", "off");
> +        connect_state.callback = callback;
> +        connect_state.opaque = opaque;
>          sock = inet_connect_opts(opts, in_progress, errp);
>      } else {
>          error_set(errp, QERR_SOCKET_CREATE_FAILED);
> diff --git a/qemu_socket.h b/qemu_socket.h
> index c47f2b0..c8431eb 100644
> --- a/qemu_socket.h
> +++ b/qemu_socket.h
> @@ -38,14 +38,19 @@ void socket_set_block(int fd);
>  void socket_set_nonblock(int fd);
>  int send_all(int fd, const void *buf, int len1);
>  
> +/* callback function for nonblocking connect
> + * vaild fd on success, negative error code on failure
> + */
> +typedef void ConnectHandler(int fd, void *opaque);
> +
>  /* New, ipv6-ready socket helper functions, see qemu-sockets.c */
>  int inet_listen_opts(QemuOpts *opts, int port_offset, Error **errp);
>  int inet_listen(const char *str, char *ostr, int olen,
>                  int socktype, int port_offset, Error **errp);
>  int inet_connect_opts(QemuOpts *opts, bool *in_progress, Error **errp);
>  int inet_connect(const char *str, Error **errp);
> -int inet_nonblocking_connect(const char *str, bool *in_progress,
> -                             Error **errp);
> +int inet_nonblocking_connect(const char *str, ConnectHandler *callback,
> +                             void *opaque, bool *in_progress, Error **errp);
>  int inet_dgram_opts(QemuOpts *opts);
>  const char *inet_strfamily(int family);

Good stuff!