Fallback to IP source address on DHCP servers not filling sid

cesanta · Jan 16, 2024 · faa5820 · faa5820
1 parent 0ad4002
commit faa5820
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Showing 2 changed files with 4 additions and 2 deletions.
diff --git a/mongoose.c b/mongoose.c
@@ -4873,7 +4873,8 @@ static void rx_dhcp_client(struct mg_tcpip_if *ifp, struct pkt *pkt) {
     ifp->state = MG_TCPIP_STATE_UP, ifp->ip = 0;
   } else if (msgtype == 2 && ifp->state == MG_TCPIP_STATE_UP && ip && gw &&
              lease) {                                 // DHCPOFFER
-    tx_dhcp_request_sel(ifp, ip, pkt->dhcp->siaddr);  // select IP, (4.4.1)
+    // select IP, (4.4.1) (fallback to IP source addr on foul play)
+    tx_dhcp_request_sel(ifp, ip, pkt->dhcp->siaddr ? pkt->dhcp->siaddr : pkt->ip->src);
     ifp->state = MG_TCPIP_STATE_REQ;                  // REQUESTING state
   } else if (msgtype == 5) {                          // DHCPACK
     if (ifp->state == MG_TCPIP_STATE_REQ && ip && gw && lease) {  // got an IP

diff --git a/src/net_builtin.c b/src/net_builtin.c
@@ -398,7 +398,8 @@ static void rx_dhcp_client(struct mg_tcpip_if *ifp, struct pkt *pkt) {
     ifp->state = MG_TCPIP_STATE_UP, ifp->ip = 0;
   } else if (msgtype == 2 && ifp->state == MG_TCPIP_STATE_UP && ip && gw &&
              lease) {                                 // DHCPOFFER
-    tx_dhcp_request_sel(ifp, ip, pkt->dhcp->siaddr);  // select IP, (4.4.1)
+    // select IP, (4.4.1) (fallback to IP source addr on foul play)
+    tx_dhcp_request_sel(ifp, ip, pkt->dhcp->siaddr ? pkt->dhcp->siaddr : pkt->ip->src);
     ifp->state = MG_TCPIP_STATE_REQ;                  // REQUESTING state
   } else if (msgtype == 5) {                          // DHCPACK
     if (ifp->state == MG_TCPIP_STATE_REQ && ip && gw && lease) {  // got an IP