patacongo commented on a change in pull request #1052:
URL: https://github.com/apache/incubator-nuttx/pull/1052#discussion_r425511715
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File path: drivers/wireless/gs2200m.c
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@@ -85,6 +85,7 @@
#define NRESPMSG (16 + 2)
#define MAX_PKT_LEN 1500
+#define MAX_PAYLOAD (MAX_PKT_LEN - 36)
Review comment:
You should not hardcode the number 36.
What is this numberanyway. It should:
The size of the Ethernet header (14) +
The size of IPv4 or IPv6 header (20 or 40) +
Any other headers.
See:
ethernet.h:#define ETH_HDRLEN 14 /* Header size: 2*6 + 2 */
ip.h:# define IPv4_HDRLEN 20 /* Size of IPv4 header (without
options) */
ip.h:# define IPv6_HDRLEN 40 /* Size of IPv6 header */
The IP headers can be longer if there are options included in the IP header.
The correct calculation can be a little complex.
But 36 does not see right? Is there a 2 byte FCS? Shouldn't this handle
IPv6 too?
Let's not use hard-coded values.
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