Re: [PATCHv8 03/15] net/lwip: implement dns cmd

[Ilias Apalodimas <ilias.apalodimas@linaro.org>]

On Fri, Sep 08, 2023 at 07:53:08PM +0600, Maxim Uvarov wrote:
> U-Boot recently got support for an alternative network stack using LWIP.
> Replace dns command with the LWIP variant while keeping the output and
> error messages identical.
>
> Signed-off-by: Maxim Uvarov <maxim.uvarov@linaro.org>
> ---
>  include/net/lwip.h           | 19 +++++++++++
>  net/lwip/Makefile            |  2 ++
>  net/lwip/apps/dns/lwip-dns.c | 63 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 84 insertions(+)
>  create mode 100644 include/net/lwip.h
>  create mode 100644 net/lwip/apps/dns/lwip-dns.c
>
> diff --git a/include/net/lwip.h b/include/net/lwip.h
> new file mode 100644
> index 0000000000..ab3db1a214
> --- /dev/null
> +++ b/include/net/lwip.h
> @@ -0,0 +1,19 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +int do_lwip_dns(struct cmd_tbl *cmdtp, int flag, int argc,
> +		char *const argv[]);
> +
> +/**
> + * ulwip_dns() - creates the DNS request to resolve a domain host name
> + *
> + * This function creates the DNS request to resolve a domain host name. Function
> + * can return immediately if previous request was cached or it might require
> + * entering the polling loop for a request to a remote server.
> + *
> + * @name:    dns name to resolve
> + * @varname: (optional) U-Boot variable name to store the result
> + * Returns: ERR_OK(0) for fetching entry from the cache
> + *          -EINPROGRESS success, can go to the polling loop
> + *          Other value < 0, if error
> + */
> +int ulwip_dns(char *name, char *varname);
> diff --git a/net/lwip/Makefile b/net/lwip/Makefile
> index 3fd5d34564..5d8d5527c6 100644
> --- a/net/lwip/Makefile
> +++ b/net/lwip/Makefile
> @@ -62,3 +62,5 @@ obj-$(CONFIG_NET) += lwip-external/src/netif/ethernet.o
>
>  obj-$(CONFIG_NET) += port/if.o
>  obj-$(CONFIG_NET) += port/sys-arch.o
> +
> +obj-y += apps/dns/lwip-dns.o
> diff --git a/net/lwip/apps/dns/lwip-dns.c b/net/lwip/apps/dns/lwip-dns.c
> new file mode 100644
> index 0000000000..b340302f2c
> --- /dev/null
> +++ b/net/lwip/apps/dns/lwip-dns.c
> @@ -0,0 +1,63 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * (C) Copyright 2023 Linaro Ltd. <maxim.uvarov@linaro.org>
> + */
> +
> +#include <common.h>
> +#include <command.h>
> +#include <console.h>
> +
> +#include <lwip/dns.h>
> +#include <lwip/ip_addr.h>
> +
> +#include <net/ulwip.h>
> +
> +static void dns_found_cb(const char *name, const ip_addr_t *ipaddr, void *callback_arg)
> +{
> +	char *varname = (char *)callback_arg;
> +	char *ipstr = ip4addr_ntoa(ipaddr);
> +
> +	if (varname)
> +		env_set(varname, ipstr);
> +	log_info("resolved %s to %s\n",  name, ipstr);
> +	ulwip_exit(0);
> +}
> +
> +int ulwip_dns(char *name, char *varname)
> +{
> +	int err;
> +	ip_addr_t ipaddr; /* not used */
> +	ip_addr_t dns1;
> +	ip_addr_t dns2;
> +	char *dnsenv = env_get("dnsip");
> +	char *dns2env = env_get("dnsip2");
> +
> +	if (!dnsenv && !dns2env) {
> +		log_err("nameserver is not set with dnsip and dnsip2 vars\n");
> +		return -ENOENT;
> +	}
> +
> +	if (!dnsenv)
> +		log_warning("dnsip var is not set\n");
> +	if (!dns2env)
> +		log_warning("dnsip2 var is not set\n");
> +
> +	dns_init();
> +
> +	if (ipaddr_aton(dnsenv, &dns1))
> +		dns_setserver(0, &dns1);
> +
> +	if (ipaddr_aton(dns2env, &dns2))
> +		dns_setserver(1, &dns2);

env_get will return NULL if any of these is not set.  Looking at
ipaddr_aton() of lwip that might lead to a NULL deref in ip_2_ip6()

> +
> +	err = dns_gethostbyname(name, &ipaddr, dns_found_cb, varname);
> +	if (err == ERR_OK)
> +		dns_found_cb(name, &ipaddr, varname);
> +
> +	/* convert lwIP ERR_INPROGRESS to U-Boot -EINPROGRESS */
> +	if (err == ERR_INPROGRESS)
> +		err = -EINPROGRESS;
> +
> +	return err;
> +}
> --
> 2.30.2
>