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Reuse server DHCPOFFER transaction id in DHCPREQUEST #1061

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Merged
merged 3 commits into from
Aug 31, 2025
Merged

Reuse server DHCPOFFER transaction id in DHCPREQUEST #1061

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2a3aff9
Reuse server DHCPOFFER transaction id in DHCPREQUEST
simonborje May 10, 2025
b704540
Remove redundant offer_transaction_id
simonborje Aug 28, 2025
48d10eb
Avoid generating unused xid:s
simonborje Aug 29, 2025
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13 changes: 7 additions & 6 deletions src/socket/dhcpv4.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -574,13 +574,9 @@ impl<'a> Socket<'a> {
// 0x0f * 4 = 60 bytes.
const MAX_IPV4_HEADER_LEN: usize = 60;

// We don't directly modify self.transaction_id because sending the packet
// may fail. We only want to update state after successfully sending.
let next_transaction_id = Self::random_transaction_id(cx);

let mut dhcp_repr = DhcpRepr {
message_type: DhcpMessageType::Discover,
transaction_id: next_transaction_id,
transaction_id: self.transaction_id,
secs: 0,
client_hardware_address: ethernet_addr,
client_ip: Ipv4Address::UNSPECIFIED,
Expand Down Expand Up @@ -624,6 +620,9 @@ impl<'a> Socket<'a> {
return Ok(());
}

let next_transaction_id = Self::random_transaction_id(cx);
dhcp_repr.transaction_id = next_transaction_id;

// send packet
net_debug!(
"DHCP send DISCOVER to {}: {:?}",
Expand Down Expand Up @@ -666,7 +665,6 @@ impl<'a> Socket<'a> {
+ (self.retry_config.initial_request_timeout << (state.retry as u32 / 2));
state.retry += 1;

self.transaction_id = next_transaction_id;
Ok(())
}
ClientState::Renewing(state) => {
Expand All @@ -692,6 +690,9 @@ impl<'a> Socket<'a> {
dhcp_repr.message_type = DhcpMessageType::Request;
dhcp_repr.client_ip = state.config.address.address();

let next_transaction_id = Self::random_transaction_id(cx);
dhcp_repr.transaction_id = next_transaction_id;

net_debug!("DHCP send renew to {}: {:?}", ipv4_repr.dst_addr, dhcp_repr);
ipv4_repr.payload_len = udp_repr.header_len() + dhcp_repr.buffer_len();
emit(cx, (ipv4_repr, udp_repr, dhcp_repr))?;
Expand Down