net: pkt: Account for IP header length for allowable payload data

nxa22042 · Anas Nashif · commit 687bd0d71090 · 2017-11-28T12:30:01.000-05:00
For calculating amount of payload data that can be added in a packet,
we need to subtract IPv6 or IPv4 header lengths from MTU.

Signed-off-by: Vakul Garg &lt;vakul.garg@nxp.com&gt;
diff --git a/subsys/net/ip/net_pkt.c b/subsys/net/ip/net_pkt.c
@@ -535,10 +535,12 @@ static struct net_pkt *net_pkt_get(struct k_mem_slab *slab,
 
 		if (IS_ENABLED(CONFIG_NET_IPV6) && family == AF_INET6) {
 			data_len = max(iface_len, NET_IPV6_MTU);
+			data_len -= NET_IPV6H_LEN;
 		}
 
 		if (IS_ENABLED(CONFIG_NET_IPV4) && family == AF_INET) {
 			data_len = max(iface_len, NET_IPV4_MTU);
+			data_len -= NET_IPV4H_LEN;
 		}
 
 		proto = net_context_get_ip_proto(context);

Original file line number	Diff line number	Diff line change
`@@ -535,10 +535,12 @@ static struct net_pkt net_pkt_get(struct k_mem_slab slab,`
`535`	`535`
`536`	`536`	`if (IS_ENABLED(CONFIG_NET_IPV6) && family == AF_INET6) {`
`537`	`537`	`data_len = max(iface_len, NET_IPV6_MTU);`
	`538`	`+ data_len -= NET_IPV6H_LEN;`
`538`	`539`	`}`
`539`	`540`
`540`	`541`	`if (IS_ENABLED(CONFIG_NET_IPV4) && family == AF_INET) {`
`541`	`542`	`data_len = max(iface_len, NET_IPV4_MTU);`
	`543`	`+ data_len -= NET_IPV4H_LEN;`
`542`	`544`	`}`
`543`	`545`
`544`	`546`	`proto = net_context_get_ip_proto(context);`