[lxc-devel] [PATCH] find veth name for unprivileged containers

[Serge Hallyn]

Quoting S.Çağlar Onur (caglar at 10ur.org):
> unprivileged containers uses lxc-user-nic to create the underlying
> network. And because of that reason netdev struct misses some
> information (like the name of the interface seen from the host side)
> 
> Find that information by parsing /proc/self/net/dev and return to
> caller.
> 
> With this patch lxc-info starts to show network stats for unpriv.
> containers.
> 
> lxc-info -n rubik
> Name:           rubik
> State:          RUNNING
> PID:            6054
> IP:             10.0.3.119
> CPU use:        0.97 seconds
> BlkIO use:      0 bytes
> Memory use:     6.52 MiB
> KMem use:       0 bytes
> Link:           veth5YTBDK
>  TX bytes:      3.41 KiB
>   RX bytes:      8.54 KiB
>    Total bytes:   11.95 KiB
> 
> Signed-off-by: S.Çağlar Onur <caglar at 10ur.org>
> ---
>  src/lxc/confile.c | 16 +++++++++++-----
>  src/lxc/utils.c   | 25 +++++++++++++++++++++++++
>  src/lxc/utils.h   |  2 ++
>  3 files changed, 38 insertions(+), 5 deletions(-)
> 
> diff --git a/src/lxc/confile.c b/src/lxc/confile.c
> index fa263ef..5794220 100644
> --- a/src/lxc/confile.c
> +++ b/src/lxc/confile.c
> @@ -931,7 +931,7 @@ static int config_hook(const char *key, const char *value,
>  				 struct lxc_conf *lxc_conf)
>  {
>  	char *copy;
> -	
> +
>  	if (!value || strlen(value) == 0)
>  		return lxc_clear_hooks(lxc_conf, key);
>  
> @@ -2002,10 +2002,16 @@ static int lxc_get_item_nic(struct lxc_conf *c, char *retv, int inlen,
>  		}
>  	} else if (strcmp(p1, "veth.pair") == 0) {
>  		if (netdev->type == LXC_NET_VETH) {
> -			strprint(retv, inlen, "%s",
> -				 netdev->priv.veth_attr.pair ?
> -				  netdev->priv.veth_attr.pair :
> -				  netdev->priv.veth_attr.veth1);
> +			if (am_unpriv()) {
> +				char *veth = find_veth_name();
> +				strprint(retv, inlen, "%s", veth);
> +				if (veth)
> +					free(veth);
> +			} else {
> +				strprint(retv, inlen, "%s", netdev->priv.veth_attr.pair ?
> +					netdev->priv.veth_attr.pair :
> +					netdev->priv.veth_attr.veth1);
> +			}
>  		}
>  	} else if (strcmp(p1, "vlan") == 0) {
>  		if (netdev->type == LXC_NET_VLAN) {
> diff --git a/src/lxc/utils.c b/src/lxc/utils.c
> index 3dff104..d82c704 100644
> --- a/src/lxc/utils.c
> +++ b/src/lxc/utils.c
> @@ -1175,3 +1175,28 @@ uint64_t fnv_64a_buf(void *buf, size_t len, uint64_t hval)
>  
>  	return hval;
>  }
> +
> +char* find_veth_name(void)
> +{
> +	int len;
> +	FILE *fp;
> +	char buf[255], *substr = NULL, *semicolon, *str;
> +
> +	fp = fopen("/proc/self/net/dev", "r");
> +	if (!fp)
> +		return NULL;
> +
> +	while (fgets(buf, 255, fp)) {
> +		if ((str = strstr(buf, "veth")) != NULL) {

This appears to be broken right now, but one day the user should be
able to start two devices, eth0 and eth1...  So I think the whole
netdev->name should be compared.  Do you agree?

Another approach (a bit more coding work but perhaps more correct) would
be for lxc-user-nic to pass the device and pair names back to lxc.
Presumably over stdout.

> +			semicolon = strchr(str, ':');
> +			len = semicolon ? (semicolon - str) : strlen(str);
> +
> +			substr = malloc(len+1);
> +			memcpy(substr, str, len);
> +			substr[len] = '\0';
> +		}
> +	}
> +	fclose(fp);
> +
> +    return substr;
> +}
> diff --git a/src/lxc/utils.h b/src/lxc/utils.h
> index f541253..08cc41c 100644
> --- a/src/lxc/utils.h
> +++ b/src/lxc/utils.h
> @@ -275,4 +275,6 @@ extern bool dir_exists(const char *path);
>  
>  #define FNV1A_64_INIT ((uint64_t)0xcbf29ce484222325ULL)
>  uint64_t fnv_64a_buf(void *buf, size_t len, uint64_t hval);
> +
> +extern char* find_veth_name(void);
>  #endif
> -- 
> 1.8.3.2
> 
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