From: Daniel Lenski <dlenski@gmail.com>
Date: Fri, 23 Apr 2021 01:58:03 +0000 (-0700)
Subject: Split ESP checksum functions into csum_partial and csum_finish
X-Git-Tag: v8.20~249
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=4b3c6c1130ed8ff97090ac896dd1a1adb88ac40d;p=users%2Fdwmw2%2Fopenconnect.git

Split ESP checksum functions into csum_partial and csum_finish

csum_partial() feeds more uint16_t words into the checksummer;
csum_finish() does the final condensation down to uint16_t, and
conversion to network order.

[dwmw2: Note this still doesn't cope with odd-sized packets but
        we don't care for now.]

Signed-off-by: Daniel Lenski <dlenski@gmail.com>
---

diff --git a/gpst.c b/gpst.c
index c3d0b5ed..d5c42890 100644
--- a/gpst.c
+++ b/gpst.c
@@ -1306,16 +1306,26 @@ int gpst_mainloop(struct openconnect_info *vpninfo, int *timeout, int readable)
 }
 
 #ifdef HAVE_ESP
-static uint16_t csum(uint16_t *buf, int nwords)
+static inline uint32_t csum_partial(uint16_t *buf, int nwords)
 {
 	uint32_t sum = 0;
 	for(sum=0; nwords>0; nwords--)
 		sum += ntohs(*buf++);
+	return sum;
+}
+
+static inline uint16_t csum_finish(uint32_t sum)
+{
 	sum = (sum >> 16) + (sum &0xffff);
 	sum += (sum >> 16);
 	return htons((uint16_t)(~sum));
 }
 
+static inline uint16_t csum(uint16_t *buf, int nwords)
+{
+	return csum_finish(csum_partial(buf, nwords));
+}
+
 static char magic_ping_payload[16] = "monitor\x00\x00pan ha ";
 
 int gpst_esp_send_probes(struct openconnect_info *vpninfo)