add boot partition size

hc

2023-12-11 d2ccde1c8e90d38cee87a1b0309ad2827f3fd30d

 kernel/samples/bpf/xdp_adjust_tail_kern.c
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@@ -18,19 +18,22 @@
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 #include <linux/if_vlan.h>
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 #include <linux/ip.h>
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 #include <linux/icmp.h>
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-#include "bpf_helpers.h"
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+#include <bpf/bpf_helpers.h>
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 #define DEFAULT_TTL 64
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 #define MAX_PCKT_SIZE 600
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 #define ICMP_TOOBIG_SIZE 98
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 #define ICMP_TOOBIG_PAYLOAD_SIZE 92
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-struct bpf_map_def SEC("maps") icmpcnt = {
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-	.type = BPF_MAP_TYPE_ARRAY,
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-	.key_size = sizeof(__u32),
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-	.value_size = sizeof(__u64),
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-	.max_entries = 1,
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-};
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+/* volatile to prevent compiler optimizations */
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+static volatile __u32 max_pcktsz = MAX_PCKT_SIZE;
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+
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+struct {
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+	__uint(type, BPF_MAP_TYPE_ARRAY);
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+	__type(key, __u32);
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+	__type(value, __u64);
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+	__uint(max_entries, 1);
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+} icmpcnt SEC(".maps");
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 static __always_inline void count_icmp(void)
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 {
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@@ -92,7 +95,7 @@
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 	orig_iph = data + off;
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 	icmp_hdr->type = ICMP_DEST_UNREACH;
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 	icmp_hdr->code = ICMP_FRAG_NEEDED;
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-	icmp_hdr->un.frag.mtu = htons(MAX_PCKT_SIZE-sizeof(struct ethhdr));
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+	icmp_hdr->un.frag.mtu = htons(max_pcktsz - sizeof(struct ethhdr));
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 	icmp_hdr->checksum = 0;
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 	ipv4_csum(icmp_hdr, ICMP_TOOBIG_PAYLOAD_SIZE, &csum);
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 	icmp_hdr->checksum = csum;
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@@ -121,7 +124,7 @@
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 	int pckt_size = data_end - data;
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 	int offset;
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-	if (pckt_size > MAX_PCKT_SIZE) {
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+	if (pckt_size > max(max_pcktsz, ICMP_TOOBIG_SIZE)) {
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 		offset = pckt_size - ICMP_TOOBIG_SIZE;
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 		if (bpf_xdp_adjust_tail(xdp, 0 - offset))
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 			return XDP_PASS;