net: avoid address-of-packed-member error

sandbox_defconfig does not compile using GCC 9.2.1:

net/net.c: In function ‘net_process_received_packet’:
net/net.c:1288:23: error: taking address of packed member of ‘struct
ip_udp_hdr’ may result in an unaligned pointer value
[-Werror=address-of-packed-member]
 1288 |    sumptr = (ushort *)&(ip->udp_src);
      |                       ^~~~~~~~~~~~~~

Avoid the error by using a u8 pointer instead of an u16 pointer and
in-lining ntohs().

Simplify the checksumming of the last message byte.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>

diff --git a/net/net.c b/net/net.c
index 5114364..5199d67 100644 (file)
--- a/net/net.c
+++ b/net/net.c
@@ -1271,7 +1271,7 @@ void net_process_received_packet(uchar *in_packet, int len)
 #ifdef CONFIG_UDP_CHECKSUM
                if (ip->udp_xsum != 0) {
                        ulong   xsum;
-                       ushort *sumptr;
+                       u8 *sumptr;
                        ushort  sumlen;
 
                        xsum  = ip->ip_p;
@@ -1282,22 +1282,16 @@ void net_process_received_packet(uchar *in_packet, int len)
                        xsum += (ntohl(ip->ip_dst.s_addr) >>  0) & 0x0000ffff;
 
                        sumlen = ntohs(ip->udp_len);
-                       sumptr = (ushort *)&(ip->udp_src);
+                       sumptr = (u8 *)&ip->udp_src;
 
                        while (sumlen > 1) {
-                               ushort sumdata;
-
-                               sumdata = *sumptr++;
-                               xsum += ntohs(sumdata);
+                               /* inlined ntohs() to avoid alignment errors */
+                               xsum += (sumptr[0] << 8) + sumptr[1];
+                               sumptr += 2;
                                sumlen -= 2;
                        }
-                       if (sumlen > 0) {
-                               ushort sumdata;
-
-                               sumdata = *(unsigned char *)sumptr;
-                               sumdata = (sumdata << 8) & 0xff00;
-                               xsum += sumdata;
-                       }
+                       if (sumlen > 0)
+                               xsum += (sumptr[0] << 8) + sumptr[0];
                        while ((xsum >> 16) != 0) {
                                xsum = (xsum & 0x0000ffff) +
                                       ((xsum >> 16) & 0x0000ffff);