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

[Orit Wasserman <owasserm@redhat.com>]

On 09/13/2012 04:22 PM, Markus Armbruster wrote:
> 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?
can't see a scenario , but it never hurt to check. 
> 
>> +        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.
> 
I think you caught a bug , i will fix it ...
Orit

>> +}
>> +
>> +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!
>