s is NULL, the IP address of the outgoing network interface is filled in as source address. If the destination IP address is LWIP_IP_HDRINCL, p is assumed to already include an IP header and p-&gt;payload points to it instead of the data.</p>
<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramname">p</td><td>the packet to send (p-&gt;payload points to the data, e.g. next protocol header; if dest == LWIP_IP_HDRINCL, p already includes an IP header and p-&gt;payload po