[CRIU] [PATCHv3 4/8] util: Enable hostname resolution of tcp address

[Andrei Vagin]

On Tue, Sep 04, 2018 at 10:26:53PM +0100, Radostin Stoyanov wrote:
> Add hostname resolution in setup_tcp_client(). This change allows a
> valid hostname to be provided as value for the --address option when
> connecting to page server.
> 
> Signed-off-by: Radostin Stoyanov <rstoyanov1 at gmail.com>
> ---
>  Documentation/criu.txt |  2 +-
>  criu/include/util.h    |  2 +-
>  criu/util.c            | 56 +++++++++++++++++++++++++++++++-----------
>  3 files changed, 44 insertions(+), 16 deletions(-)
> 
> diff --git a/Documentation/criu.txt b/Documentation/criu.txt
> index 6bb3f0f5..04e7a610 100644
> --- a/Documentation/criu.txt
> +++ b/Documentation/criu.txt
> @@ -550,7 +550,7 @@ Launches *criu* in page server mode.
>      It isn't supposed to use --daemon and --status-fd together.
>  
>  *--address* 'address'::
> -    Page server IP address.
> +    Page server IP address or hostname.
>  
>  *--port* 'number'::
>      Page server port number.
> diff --git a/criu/include/util.h b/criu/include/util.h
> index b286b3e9..aba16818 100644
> --- a/criu/include/util.h
> +++ b/criu/include/util.h
> @@ -293,7 +293,7 @@ void print_data(unsigned long addr, unsigned char *data, size_t size);
>  
>  int setup_tcp_server(char *type, char *addr, unsigned short *port);
>  int run_tcp_server(bool daemon_mode, int *ask, int cfd, int sk);
> -int setup_tcp_client(char *addr);
> +int setup_tcp_client(char *hostname);
>  
>  #define LAST_PID_PATH		"sys/kernel/ns_last_pid"
>  #define PID_MAX_PATH		"sys/kernel/pid_max"
> diff --git a/criu/util.c b/criu/util.c
> index 71bb2f6e..5c9fb306 100644
> --- a/criu/util.c
> +++ b/criu/util.c
> @@ -30,6 +30,7 @@
>  #include <sys/resource.h>
>  #include <sys/wait.h>
>  #include <sys/socket.h>
> +#include <netdb.h>
>  #include <netinet/in.h>
>  #include <netinet/tcp.h>
>  #include <sched.h>
> @@ -1384,28 +1385,55 @@ out:
>  	return -1;
>  }
>  
> -int setup_tcp_client(char *addr)
> +int setup_tcp_client(char *hostname)
>  {
>  	struct sockaddr_storage saddr;
> -	int sk;
> -
> -	pr_info("Connecting to server %s:%u\n", addr, opts.port);
> +	struct addrinfo addr_criteria, *addr_list, *p;
> +	char ipstr[INET6_ADDRSTRLEN];
> +	int sk = -1;
> +	void *ip;
>  
> -	if (get_sockaddr_in(&saddr, addr, opts.port))
> -		return -1;
> +	memset(&addr_criteria, 0, sizeof(addr_criteria));
> +	addr_criteria.ai_family = AF_UNSPEC;
> +	addr_criteria.ai_socktype = SOCK_STREAM;
> +	addr_criteria.ai_protocol = IPPROTO_TCP;
>  
> -	sk = socket(saddr.ss_family, SOCK_STREAM, IPPROTO_TCP);
> -	if (sk < 0) {
> -		pr_perror("Can't create socket");
> -		return -1;
> +	if (getaddrinfo(hostname, NULL, &addr_criteria, &addr_list)) {
> +		pr_perror("Failed to resolve hostname: %s", hostname);
> +		goto out;
>  	}
>  
> -	if (connect(sk, (struct sockaddr *)&saddr, sizeof(saddr)) < 0) {
> -		pr_perror("Can't connect to server");
> -		close(sk);
> -		return -1;
> +	for(p = addr_list; p != NULL; p = p->ai_next) {
> +
> +		if (p->ai_family == AF_INET) {
> +			struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ai_addr;
> +			ip = &(ipv4->sin_addr);
> +		} else {
> +			struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)p->ai_addr;
> +			ip = &(ipv6->sin6_addr);
> +		}
> +
> +		inet_ntop(p->ai_family, ip, ipstr, sizeof(ipstr));
> +		pr_info("Connecting to server %s:%u\n", ipstr, opts.port);
> +
> +		if (get_sockaddr_in(&saddr, ipstr, opts.port))
> +			goto out;
> +
> +		sk = socket(saddr.ss_family, SOCK_STREAM, IPPROTO_TCP);
> +		if (sk < 0) {
> +			pr_perror("Can't create socket");
> +			goto out;
> +		}
> +
> +		if (connect(sk, (struct sockaddr *)&saddr, sizeof(saddr)) < 0) {
> +			pr_info("Can't connect to server %s:%u\n", ipstr, opts.port);
> +			close(sk);
> +			sk = -1;
> +		}

How many sockets are we going to create? Why do we need this loop?

>  	}
>  
> +out:
> +	freeaddrinfo(addr_list);
>  	return sk;
>  }
>  
> -- 
> 2.17.1
> 
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