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

[Maxim Uvarov]

On Wed, 13 Sept 2023 at 14:32, Simon Goldschmidt <goldsimon at gmx.de> wrote:

>
>
> On 13.09.2023 07:56, Ilias Apalodimas wrote:
> > 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 at 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 at 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()
>
> Looking at the NULL checks in ipaddr_aton(), you found a bug in lwIP.
> I'd vote to leave the above code as is and rely on the bug being fixed
> in lwIP before U-Boot enables IPv6 (this is only a bug in dual-stack
> mode where IPv4 and IPv6 is enabled).
>
> Regards,
> Simon
>
>
Yes, I looked for an ipv4 case with null check.  But I think here we can go
with:
if (dns2env && ipaddr_aton(dns2env, &dns2))



> >
> >> +
> >> +    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
> >>
>