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embassy-net: dns: bound the dns_servers slice

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`smoltcp::socket::dns::Socket::update_servers()` will
panic if a slice exceeding a fixed length is passed
to it. This is can be especially inconvenient when
using DHCP config.

Avoid panicking by using at most `DNS_MAX_SERVER_COUNT`
DNS servers from the config.
This commit is contained in:
Gasper Stukelj 2024-07-28 21:50:52 +02:00
parent e54c753537
commit c5d077a2c6
1 changed files with 13 additions and 3 deletions
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16
embassy-net/src/lib.rs
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@ -34,6 +34,8 @@ use embassy_sync::waitqueue::WakerRegistration;
use embassy_time::{Instant, Timer};
#[allow(unused_imports)]
use heapless::Vec;
#[cfg(feature = "dns")]
pub use smoltcp::config::DNS_MAX_SERVER_COUNT;
#[cfg(feature = "igmp")]
pub use smoltcp::iface::MulticastError;
#[allow(unused_imports)]
@ -823,9 +825,17 @@ impl<D: Driver> Inner<D> {
// Apply DNS servers
#[cfg(feature = "dns")]
s.sockets
.get_mut::<smoltcp::socket::dns::Socket>(self.dns_socket)
.update_servers(&dns_servers[..]);
if !dns_servers.is_empty() {
let count = if dns_servers.len() > DNS_MAX_SERVER_COUNT {
warn!("Number of DNS servers exceeds DNS_MAX_SERVER_COUNT, truncating list.");
DNS_MAX_SERVER_COUNT
} else {
dns_servers.len()
};
s.sockets
.get_mut::<smoltcp::socket::dns::Socket>(self.dns_socket)
.update_servers(&dns_servers[..count]);
}
self.config_waker.wake();
}